Oh, who cares about user number now?
It only really matters with cutoff points.
Like right now, if there are, say, 5000 regular board members and we're all migrating over to this new board now, then that means everyone with a number between 1 and 5000 is equally old, as far as this board is concerned.
Then from now on, your user number above 5000 indicates when you joined. Like maybe the 5100-5200 are those who joined in February of 2002. 6000+ means you joined 2003, etc.
So all numbers below 5000 are actually identical, so who cares which one you get?