> What do you expect Nvidia to do, post armed guards in Asia to make sure the GPUs don't move around?

Yes. Some companies that deal in export restricted items will have entire teams of US citizens that regularly do inventory checks in foreign customers facilities. If a single item is missing and it can't be located within 24 hours they pack everything up and put it on a cargo plane back to the US.

It is a trivial amount of money when you are talking about $100m+ deals.