My trust in reviews run about the same as my trust in used car salesmen.
Many reviewers have been linked to certain camera manufactures. Others are just camera junkies who get off on coming across as serious reviewers.
If I made decisions based on reviewers I would not buy any equipment as most of the time I have found a split between those that like the product and those that do not.
This review is no different.
Thanks for sharing, I now understand where your misinformation came from.

I have used Photography Life to inform many of my purchase decisions. My experience is that he is a photographer first, and understands how to test and has a proper testing environment. Compared to other "reviewers" his have been on target, accurate and reliable. When he states that lower priced lenses are prone to sample variations, in my 53 yrs of experience as a photographer, I can say that his observations are completely believable. Your disagreement is not. Keep in mind Mansurov reviews and tests many lenses, and is simply reporting observed variation, which he finds to be an issue with lower cost lenses.

So, although you state you are not an expert, but you know very little about Mansurov and his testing methods, a highly regarded reviewer with complete transparency - he even states that he gets revenue support from retailers - Adorama, B&H and Amazon - and not specific camera or lens mfgrs - yet you have an issue with his review. As far as your claim that knowing the process and equipment used to manufacture something has anything to do with the result - sample variation - shows a lack of knowledge on your part. In fact, the issue is probably more statistical in nature. How a mfgr manages its QC, not testing enough to ensure a lower sample variation rate. If a mfgr chooses to use a lower testing frequency for mass produced items, then it is logical that there will be higher sample variation. In the case of premium very expensive lenses you can bet that part of the price has a lot to with the TLC these products receive during manufacturing and later with a much higher sample testing frequency, which in turn results in fewer bad copies being released for sale.

FWIW - this is the actual representation Photography Life made regarding quality control and sample variation:

"Quality Assurance / Sample Variation
When a lens with such a huge zoom range and low price point is made, it is safe to assume that there are always going to be compromises. Lenses can suffer from all kinds of problems – from de-centering of lens elements and focus accuracy issues, all the way to poor construction practices, which can go undetected during the quality assurance process.

We have seen this with the Tamron and Sigma 150-600mm lenses, which can be a bit of a gamble in terms of sample variation. Good samples can produce excellent results, while bad ones will make the experience of owning a lens pretty frustrating. Since sample variation is a big problem for properly evaluating and testing lenses, our team at PL always strives to test at least several copies of the same lens. In the case of the Nikon 200-500mm f/5.6E VR, we used two brand new samples of the lens to measure its optical performance in a lab environment, while using a total of 5 lens samples to test them in the field. My personal goal was to see how much variation there is on the 200-500mm VR and how it compares to the experience our team had with the Tamron and Sigma counterparts.

Unfortunately, the 200-500mm VR did not turn out to be any better than the 150-600mm competitors in terms of consistency. The lens sample that John Sherman used for his testing turned out to be quite poor when shooting at infinity (as reported in his detailed super telephoto zoom lens comparison), which I did not experience with mine. Tom Redd’s first sample of the 200-500mm was “horrible” in terms of sharpness, so he had to swap his out for another sample, which turned out to be quite a bit better.

My sample, along with John Lawson’s sample were quite decent from the get-go. So out of the 5 total samples, two turned out to be duds from the start, which is not a particularly encouraging statistic. Perhaps we have had bad luck, but like I have said earlier, at this zoom and price ranges, there will always be compromises. Hence, you should not pick one brand over another based on build quality – it looks like they are all built in a similar fashion, with potential variance issues from sample to sample. As I always recommend, make sure to test each lens you purchase before fully committing to it – a simple focus test or a de-centering test can quickly reveal serious optical issues…"

I suggest you read the article, since it seems that you have not. I suspect your level of confidence may actually go up. . . One thing is certain, he is no Ken Rockwell. . .