> With public auctions, my understanding is they only need to pay attention to the domains someone actually tries to register. So if I'm China, I don't need to preemptively register the entire space of `/tiananmen/g`. I only need to download the list of auctions every day and run a regex on that finite space.

Sure, but since it doesn't cost anything to lose a bid (I believe?) if anyone tried that it'd be pretty easy to force them to spend a _lot_ of money buying domains that they have no intention of using. It also wouldn't stop anyone from registering `tiananmen.massacre`, as you noted.