The problem with this statement is there is no one standardized method of testing potency. Some methods use heat, which can decarboxylate the material.
There is no standard for how the material is picked for testing. Further, buds on the same plant, the same branch even, will all test out differently to each other, regardless of testing method.
Even further, commercial testing allows for labs to cover a certain amount of weight for the batch. So one single test can account for a massive batch (in terms of quantity.) So that makes a desirable test important, because it covers your "claim" for that batch.
Then lab shopping is a thing. Don't like the results of Lab A? Try Lab B! Laboratories aren't the defenders of justice or truth either, they just fulfill the service. Some labs are known for giving skewed results to retain customers, etc.
You can also doctor samples very easily; they are typically ground up for testing. So adding kief, for example, can change your numbers pretty easily and no one would be the wiser.
Testing is better than nothing, but it's a far cry from some gospel that actually dictates what the reality is. If anything, it's better for recognizing the potential of the plant, but that still requires some honesty and understanding for those numbers to even be relative.
, Yard work takes longer and that means more beer and 
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