Therefore they do not seem particularly bothered by this rejection, as it was not going to let them get the "full" version working anyway.
Well for one, they already wrote the app. If you've got the $99/year developer subscription you might as well use it for something.
And for two, the perceived slight against UTM on the App Store was the existence of a JIT compiler, which wasn't strictly essential (but very helpful for newer OSes). So disabling the JIT would at least give you novelty features, but even that version was rejected for some new, unspecified rugpull reason. Rationally, UTM doesn't want to play this game of cat-and-mouse unless Apple changes their policy to more explicitly allow their use-case.