Are those lab test certificates/COAs legit or just good marketing?

I’ve seen more vendors popping up lately advertising full lab testing attaching PDFs showing purity numbers, isomer ratios, clean results, all that.

On paper it sounds great for harm reduction, but it got me thinking: how much of this can we actually trust? Anyone with basic graphic design skills can whip up an official-looking PDF or reuse a single good lab test for months of random batches.

For people who know how these third-party testing labs actually work:

Is there any real way to check if a certificate is actually tied to the batch in your hand, or is it basically just blind trust?

Do these independent labs have public verification lookup codes, or are most people just taking a seller's word for it?

Aside from doing your own reagent / FTIR checks at home or at a local harm-reduction site, how do you guys treat these claims?

Not asking about specific sellers or sources, just curious about the testing side and whether these papers are actually worth anything.