The point is, the rest of his group continues to play while he comes back and plays the second ball. He races back out, plays to the green, finishes out and catches up with his group. Once he plays to the green, you can be hitting. It should take you all of 1/2 hole to catch up with his group again. If they all stand around waiting for your group to play through, then the next bunch behind you will already be moving toward the tee and now you have delayed more than just one group. If you have a problem with it, then play someplace where nobody cares about the rules.
I have no doubt he is a fast player - and fast at re-teeing. But he isn't faster at re-teeing than he is at not re-teeing. And he isn't long gone before I can make one swing - when he is still 250 yards from the tee box and walking out of the woods after a 5-minute long unsuccessful search for his ball. And maybe no one is behind me - so he won't be holding anyone up to let me through.
And maybe the play-through idea is not a good solution. As previously stated, it was just an idea and something I'd probably offer to someone behind me if I was holding them up in this fashion. My lost ball - my problem. You fellas go ahead through.
But I don't think it is any slower than the re-teeing that would be going on all over the course if this is really how people played it out. And maybe the rest of the course isn't as fast as David at re-teeing. And maybe they aren't as diligent about hitting a provisional as he is - which means even more re-teeing. It's gonna slow down play.
I've never seen anyone do this and I doubt it happens very often. With all I hear about slow play on the GC, the magazines, the websites, this site, etc - I really thought that golfers would sort of acquiesce that you will come up with as fair of a solution as you can without actually going back to the tee box while people are waiting on it. I even thought I understood your post earlier in this thread to say that you wouldn't go back either.
As for the rules - sure I care about them. If there is no one waiting behind, go re-tee. But when other folks have paid their money and want to get a timely round in and the lost ball is my problem - I would just try to make the best of the situation and do the next best thing that's fair to the rulebook, the handicap committee, and any opponents I might be playing with - and try not to burden the other groups.