The usual model of buyer scepticism is that unsupported claims are ignored. The observed behaviour is worse than that. A claim a buyer cannot verify is treated as evidence about the seller, and it lowers the credibility of the claims around it.
This is why adding another superlative to a page that already has several makes the page weaker. Each one dilutes the ones beside it.
What survives
Specificity that would be embarrassing if wrong. A number with a method attached. A limitation stated without being asked. A named exclusion. These work because they are costly to fake, and a buyer reads the cost.
The awkward consequence
A firm holding itself to this will publish less than its competitors and will look smaller for a period. There is no way around that. The alternative is a page of claims that a serious buyer discounts as a set, which is a slower and more expensive way to be small.