After all, not doing updates isn't the important thing, it is that the right piece of information is used at the end.

It's an important thing, in that we don't know how to do updates without getting misled in some strange situations. UDT uses other sources of information, and shows how that's sufficient in principle, but the current puzzle is how to make use of the information that UDT doesn't use, avoiding UDT's logical cornucopia (so that one has to deal with resulting logical uncertainty, and resolve it to a limited extent based on observations).