I think you've just not understood the answers you've been given multiple times:

BU does not by itself open up a new Sybil attack vector - anything you've described can be used against Core just as easily.

This will be my last post on this "Sybil attack" hobby horse. Over and out.

P.S. So far since joining this thread, I've been kicked off by the forum software once, denied login for 45s, and now throttled for posting within a 360s cool-off period.
You may find these settings useful on your forum, but they do not contribute to my good experience as a new user trying to participate in this thread.
FWIW I've never run into such limits on the other forum proposed to hold this discussion.