This also extended to families where parents could limit the time that their kids spend on games. Unfortunately it seems that kids are smarter than Apple might have given them credit for because in this post on Reddit, it appears that kids have managed to find a way around the screen time restrictions.
According to user PropellerGuy, “When iOS 12 came out I limited my 7-year old son’s screen time through the family share. For a few days I felt like he was playing a bit more than he should, but I couldn’t figure out why. Finally today, my son revealed his hack: When he runs out of screen time and his games get locked, he heads to App Store, downloads a previously installed (but later removed) game through the cloud icon, and it works without limitations! What can I say.. I’m not even mad. That’s impressive.”
Now this isn’t a bug or a hack and can actually be fixed by parents disabling “Install Apps” within Restrictions, but given that it isn’t a particularly obvious feature, it looks like some kids are taking advantage of that for now.