Basically it’s a way for a “third party” that’s chosen by the web server to verify the environment where the front end code is running meets its standards. Those standards would be up to the third party. So I’d imagine if an assessor said “hey, we can verify ads load properly” or even “we verify this extension isn’t running” then many sites would possibly choose those assessors. It also is blatantly deceitful because of all the issues it suggests it can fix, it doesn’t actually fix any of them. And many of them aren’t even that big of a problem.