I'm deeply skeptical that export controls are going to work with China if the item in question is a consumer GPU unless you're going to radically redesign the things to do something extremely obnoxious like require cryptographically-secure online activation every boot. There are just too many individuals and small businesses in random other countries who are going to be able to buy them and resell them. The chain over which a GPU travels is too far disconnected from entities that we can directly affect.

Maybe they can induce a very limited delay, or increase costs to a limited degree, but I assume that that's not what the goal is.

You can only effectively export-control something if, all along the chain from the manufacturer to the end user, you can clearly distinguish between a legit and non-legit user. There's no way that some random electronics store in Kazakhstan is going to know whether the person buying a 4090 with cash is going to sell it in China or use it themselves.