I lab tested PPL once, after being a sperg and getting into a semantics argument (I think you were in the thread at SST), and overnighted to Jano, only to come back with 98%+ lol. Basically got my ass handed to me after spending nearly $300.
To be frank, I wouldn't want to spend hundreds of dollars to test every single raw I get, waiting weeks to get a result. Which is why I'm willing to pay the extra money to go through PPL, as they have a reputation to keep.
I ask about QSC because I've never used them other than kits, and if my assumption is correct, I would be cutting out middlemen. That's all.