The fast-path TSA agents don't do the opt-out pat downs. They couldn't: the search happens in a semi-secluded area of the checkpoint, and the whole line would have to shut down if they didn't have people dedicated to that task. You do not in fact add 5 minutes for everyone else.

What is true is that you may end up in line behind 1 other person waiting for extended screening (if they don't have their ID, or if they got randomly selected), and you may add 5 minutes to those people's time. I have very little problem with that.

I'd refuse (politely) even if I knew I was screwing over the line, though. A strip search is a strip search. It crosses the line.