Even pure AI art is unenforceable unfortunately. Like any form of cheating, some will be amateurish and obvious. But others will be sophisticated, skilled, and will simply blend into a gray area where you can't easily define a line.

How much "AI tool assistance" does it take before it's called "AI generated content"? It's totally arbitrary, and in many cases it's going to be completely unenforceable.

That doesn't mean it has no value, but it does mean it's not a silver bullet and no amount of tweaking is going to make it one. We can quickly use it to take out the obvious slop, the well-crafted examples will pass beneath anyone's notice, and when examples fall into the gray area we'll all bounce around inside with arguments about who we believe and how much is normal and acceptable until we eventually reach an arbitrary, per-game consensus, or maybe adjust the "rules" a little to accommodate them, but nothing really changes, we'll probably be arguing about whether games contain "too much AI" for decades now and there will never be a clear solution or answer.

Sometimes it is, sometimes it's not. Better to make the rule and enforce it where they can than to just forget about it. Maybe some honest devs will disclose it.