I'm more of a fan when deboarding is through the forward door, and not a center door behind first. Generally, I think a good FA can make sure coach PAX do not slow down First much, and it's silly to hold off Coach from deboarding if they're not affecting First.

That said, one minute can chain into a extra five at customs and another five with baggage. If you're pitching to VC, or headed into a cabinet meeting, or being flown in to perform surgery, etc etc, that time can be critical. FWIW.