Just to clarify, correct AF has everything to do with sharpness - an out of focus image cannot be sharp. As you say, it affects focus accuracy. If one decides to do this adjustment, the main issue as I see it is a subjective judgement as to what’s in focus - I’ve tried the angled scales, and that’s the issue - trying to judge exactly which number is in the best focus. If you want an actual objective, repeatable measurement, the FoCal system by Riekan is the answer. Not only do you get an accurate AF calibration, you can also get a curve of acuity vs aperture (which I find invaluable for telling where your lens is sharpest, how much degradation from diffraction at smaller aperture and an instant measurement as to whether the new lens you just bought is up to snuff) and a graph of AF repeatability. It’s the best $90 (for the professional version) I’ve spent since I bought my first Nikormat for $125 in 1968. Of course if you’re using a MILC, then AF accuracy and MFA is no longer an issue.

This is why. In camera focus adjustments are a kluge at best - a ham-handed approach that is only a simple offset to the focus - at all distances and focal lengths by the same amount. Lenses can and should be adjusted at more than one distance and focal length - like some of the Tamrons and Sigmas because focus errors are rarely linear in nature.

The following quote right from Nikon's D850 Tips page says all you need to know:

"Use only as required. AF fine-tuning should be performed at the focus distance at which the lens is normally used; finetuning performed at short focus distances may be less effective with distant subjects and vice versa.

https://nps.nikonimaging.com/technical_solutions/d850_tips/useful/auto_af_fine-tuning/

The primary reason to have this feature, or even the manual version, is to perform a field adjustment in the event something is wrong. It was never intended to replace a proper factory calibration.

This, from Nikon again, confirms the intent of the AF Fine feature and when to use it and warns that it in the same as a factory calibration:

"AF tuning is not recommended in most situations and may interfere with normal focus; use only when required.

Service note: If your lens has a focus problem you should return it to Nikon Service as AF Fine-Tune is not intended to solve optical problems which will generally be outside of scope for this tool. If you have a focus problem which is always present with different lenses then this would indicate a camera setting issue or that the camera has received impact damage which is causing general defocus problems. Again return it to service."

https://www.nikonimgsupport.com/na/NSG_article?articleNo=000043897&configured=1&lang=en_SG

I have multiple bodies and a dozen lenses, and frankly I would feel like a dog chasing it's tail if I had to manually adjust each body for each lens. So I feel your frustration. I do trouble shoot a perceived focus error (camera or lens) and send in the offender to the mfgr - all of my lenses are tack sharp at all distances and in the case of zooms, at all focal lengths on all of my bodies without the need for AF Fine tuning.

So forget what you read on this forum. I've given you the words from the source. If you want to still believe that AF Fine tuning is a good, permanent solution to focus errors, then go right ahead believing . . .

There are two possible factory calibrations - one lens matched to one body (if you send both in AND they are both from the same manufacturer) or both adjusted independently to be within the factory tolerance. So no dimension or specification is exact - everything has a tolerance (I mention this as the quality manager for a high precision aerospace manufacturing company where we calibrate EVERYTHING). The net-net is that both the lens and the camera can be within factory tolerance, but when mated, the tolerance stack up creates an unacceptable error if max focus accuracy and sharpness is the goal. On the other hand, if you factory match every lens you own to one body, then it won’t be matched to another body, and let’s not forget the inconvenience, potential damage, cost and potential shock which can change the calibration during shipping. There is also no reason to believe that their “calibration” is anything different than applying a “blanket” change to the AF. Ideally, there would be a curve of corrections applied such as that created using some aftermarket lenses “docks”, but we have no way of knowing if the factory has this ability on all (or any) of their lenses.

Having said that, I will gladly grant that on most cameras with MFA, there are a max of two adjustments for zooms and one for primes, so not perfect as the “correction curve” that would be ideal, BUT it is very likely, if properly applied, to be preferable to no adjustment. The claim is routinely made that it can cause misfocusing (but if you don’t like the results of your calibration, just turn it off or reset to zero). It is also claimed that it is appropriate only at one distance and at one FL for zooms or can prevent focusing at infinity. Obviously, I can’t test every every possible lens, but I have tested a lens at multiple distances and infinity, and found that while the adjustment does vary some with distance, the KEY is that at every distance, it was an improvement at EVERY distance and focused fine at infinity. I published the results on UHH (https://www.uglyhedgehog.com/t-508300-1.html), and if anyone disagrees with the conclusions, I invite them to repeat the test on their lens(es) and publish the results.

For all those that claim to have never needed to adjust a lens, I would answer that without trying, one never knows if their lens can perform better or not. Needless to say, I, and many pros, do calibrate their lenses. I am in no way as good a photographer as some that do not calibrate, but I can represent that by careful calibration and measurement, I know that my lenses are delivering the max performance that they're capable of. This is one of those “religious” issues like Canon vs Nikon, PC vs Mac, etc., so those that don’t calibrate are unlikely to try it, and those that do, believe in the results they get. And of course, one has to wonder why manufacturers include this feature if it has no value when properly applied.

I have owned 3 200-500 Nikon lenses, I have NOT calibrated any of them and they were all sharp out of the box. I do not recommend calibrating ANY lenses, most make the lenses worse by doing so. This lens is already medium slow at F5.6, you should not have any issues. Even experts like David Busch recommends NOT calibrating lenses.
You bought a very nice lens, go out and shoot it. It is very sharp and should not need any calibration.
I shot the images below wide open. Good luck and keep on shooting until the end.

The adjustment in Nikon cameras has zero being on sharpness. It adjusts back and front focus. In other words making sure the camera focuses exactly where you focus it. Not a quarter inch behind or in front of or more. I am a perfectionist. I adjust all my lenses and use the sigma dock to adjust a lot of the perimeters on my sigma lens. None of the adjustments will make a lens sharper. It can make it sharp where you are actually focusing instead of slightly in front of or behind. If a lens is not sharp at any focal length then it has a defect. Usually due to decentering. You can test for that. I agree with you on everything just want the op to understand to look at his photos at 100 percent with the focus indicator on. If the photo is not sharp under the focus indicator look at the photo behind and in front of the indicator. If you see it is sharp anyplace other than the focus indicator it needs adjustment to bring the focus forward or move it backwards until it coinsides with the focus indicator. Of course the shot should be off a tripod at a high shutter speed and normally if I want to test it I use a test fixture similar to this.