The fallacy is the one I just described: attaching a utility function post hoc to what the system does and does not do.

A fallacy is a false statement. (Not all false statements are fallacies; a fallacy must also be plausible enough that someone is at risk of being deceived by it, but that doesn't matter here.) "Attaching a utility function post hoc to what the system does and does not do" is an activity. It is not a statement, so it cannot be false, and it cannot be a fallacy. You'll have to try again if you want to make sense here.

The TSUF is not a utility function.

It a function that maps world-states to utilities, so it is a utility function. You'll have to try again if you want to make sense here too.

We're nearly at the point where it's not worth my while to listen to you because you don't speak carefully enough. Can you do something to improve, please? Perhaps get a friend to review your posts, or write things one day and reread them the next before posting, or simply make an effort not to say things that are obviously false.