I have been amazed at how far I can hit the ball with what feels like a painfully slow right arm thrust (and conversely how screwed up a shot can get when I thrust "fast" -- which probably means "early").
A lot of times my swing thought is "slow, heavy, deliberate"...
I think it works because of mechanical advantage of the club still whipping through from left wrist uncocking and release of the lag. I'm still studying.
Also, remember, it's even hard for a trained eye to truly tell if someone is hitting or swinging, so the "speed" of the thrust may be more one of feeling.