True, but there's probably many ways to do this and unless AI content starts falsifying tons of its metadata (which I'm sure would have other consequences), there's definitely a way.

Plus other sites that link to the content could also give away it's date of creation, which is out of the control of the AI content.

If it's just using Google search "before <x date>" filtering I don't think there's a way to game it... but I guess that depends on whether Google uses the date that it indexed a page versus the date that a page itself declares.

"Gamed quite easily" seems like a stretch, given that the target is definitionally not moving. The search engine is fundamentally searching an immutable dataset that "just" needs to be cleaned.