My understanding is that you play the ball slightly more toward-target in the stance, and the club is slightly longer, thus the angle of descent into the ball is less. I still think the intent should be to catch the ball just before (or at) the bottom of the swing, but the descent angle will be inherently flatter.
I mush my 3w pretty well. I would never recommend trying to "hit it on the upswing." That can happen if you're thinking sweep.