This product may be as good as you say, BUT, it does not get good reviews on the B&H website from the folks who have used it. If fact, many found it to cause further problems. Nikon Techs in California and New York caution against calibrating lenses because, according to Nikon, you can only fine turn for one distance.
Nikon May only calibrate for one distance, but that is Nikon, my Canon calibrates at both the long end and short end of a zoom.
You are not calibrating the lens, you are calibrating the camera to the lens, if a problem is caused, gee, simple to reset the calibration back to zero, eliminating the “problem”.
I would wonder if the Nikon folks are talking about actually calibrating the lens, which would be far more work, expense and not easily reversible vs the micro focus adjustment in camera?
I have used the FoCal software very successfully on my Canon with Tamron, Sigma & Canon lenses, and am very happy with the results. BTW - MY 16-300 Tamron required a large adjustment, -15 on the long end, my Canon zoom lenses, 0 on the long & short end.
The report generated for each lens adjusted shows the results and they are very visually clear.
Edit: I went to B&H, seems there are 31 out of 71 reviews showing 5 star reviews.
Of course reviews are always questionable since we never know if the reviewer actually learned to use the product properly.