Read the primary source rather than the write-up and the two do not agree, so here is what is actually in it.
The useful checklist is about verifiability rather than presentation. Independent test results commissioned by buyers rather than by the seller, consistency across multiple batches over time rather than one flattering report, a physical address and a company registration that resolve, batch and lot numbers on the actual labelling, and a shipping practice that matches what the material needs. Everything a good-looking website provides is cheap to fake; none of the items above are.
Where I think it is weakest: the follow-up is short relative to how long people actually take these drugs, so durability is an assumption here rather than a finding.
The bit I cannot resolve on my own is how people are distinguishing a supplier having a bad batch from a supplier on the way out. I have searched first, so if this is covered somewhere point me at it and I will read it.
Note on sourcing:
Figures above are from the primary publication rather than the press summary. If a number here disagrees with one you have, post yours and we will work out which of us is reading a secondary source.