I think the point of the 10/40 is two fold.

1. Like you said, it's to wear the opponent down while keeping your guys fresh

2. It's also meant to confuse and force quick decisions by the opponent by closing down quickly, pressuring the passing lanes and making it difficult over the half court. On offense, the quick shot makes it difficult to identify the shooter.

I think by only playing it for part of the game you sacrifice wearing the opponent down, but you do keep your own players fresh. Where the focus needs to be if we use it is #2.