The thing I have found about clipless and the "pulling up" is that it allows you to quickly rotate through muscle groups. When you need to make time the easiest way to increase your speed is to plant your rear in the saddle and focus your efforts on cadence. When you are out of the saddle it is significantly harder to pull up, your body is in a position to put pressure downward. But when you are saddled you can just focus on a smooth pedal action and it really shows.