Yeah, it’s always difficult to judge with trolls.
That’s up to the controller I guess. I personally don’t do it, the clearance is still valid after a re-sequence. Some controllers like to do this though, just to give the pilot assurance that despite their new sequence, they are still cleared.
If you re-sequence and someone is promoted to number 1, then I would re-clear, as this is the only way to directly tell the pilot that he is not following anyone anymore.