I won't say anything about Dierdorf because my mother taught me better, but that said . . .
If the punter had gotten the pass away and it fell incomplete, the ball would be returned to the original LOS provided that it was a legal pass (i.e. not intentional grounding). It wouldn't be any different than Brady or Luck scrambling around 10-20 yard behind the LOS and throwing an incomplete pass.
I think the punter's issue was that he was trying to make something happen on the fly and couldn't decide between taking a safety, trying to run, diving on the ball or trying to throw a pass. Kickers are notorious for not thinking clearly in panic situations (witness Garo Yepremian).