On top of what has already been explained, there is a somewhat common pattern. Pretend I’m a brand new seller with 1000 vials of test.
No one knows me, so I send in samples of my tear to the lab. I post results, people give me a chance and buy from me. I sell all 1000 vials.
For the next batch, I could send a sample in. But how do you know that I’m not just sending a good vial to the lab, but mailing out vials that are 85% as strong to everyone else? There’s no way to know.
That’s why vendors offer store credit for lab work. Since they don’t know which vial may end up at Janoshik for testing, if they are doing anything shady, it’s a pretty big risk. In that way, offering store credit is an even better guarantee than submitting your own samples, but has the drawback that a customer has to actually do it. The vendors who do both are rare but fucking indispensable.
That’s a long way around to say, some people get tests done when they start up, and that’s what they post. That may be from when they first opened, and you may have to look for users’ posts to find the newer, blind test results.