Here's the problem, if they do, how would they be able to tell valid old Pokemon from ages ago versus transferred inject ones with fake backgrounds?
Pokemon injecting is a lot like getting a fake ID- you falsify a bunch of numbers of code to generate the pokemon you want, but you have to make sure that its deeper data, like OT/Pokemon ID appear legit. If you do it correctly and that all checks out then there's no reason why it would be identified as hacked, flagged, and called out.
Recall back in 2015 when worlds competitor and former champion Ray Rizzo was caught with a hacked Pokemon. The reason it was discovered was not during any hack checks, in fact anytime you enter a regionals or higher VGC torunament, they do a computerized hack check (essentially the same check the game does when you played on Battlespot online). The Pokemon passed. It wasn't until some time later that someone had pointed out that his Aegislash had a dream ball, and his Ludicolo and Politoed were in Lure Balls. Because of how hidden ability/ Pokeball type mechanics were back then (dream balls only existed from gen 5 dream world, Aegislash couldn't possibly be in one in X/Y), anyone who saw this could automatically identify that these were not legit... yet they clearly passed every automated hack check available at the time.
I don't believe they could ever do it, not unless they were somehow able to cross reference a list of every single OT ID that's ever existed.