They do, but it's not "qa" in the sense of are there any bugs in the game, there's a checklist you have to adhere to and as long as you adhere to it, you're good. It mostly checks stuff like if you've got voice chat, do you respect parental controls,or are you using any undocumented APIs, or does the game crash under "normal use". An unstable game can pass these was checks, and there are no guarantees of quality from this process.

(Disclaimer: I work on Fortnite, have ample experience with making sure the rules are followed)

That makes sense, thanks.