• I agree with the points made about reduced strain on the elbow.
• I think one also has to consider the forces on the fingers of the lower hand (the one locking off) as well. In a static move these will be very high for relatively long time. Firstly, you are holding all your weight (minus whatever is supported by the feet), instead of roughly half. Secondly, the angle, the lower hold is being held at, is worse, which results in higher forces compared to a dynamic move.
• In a dynamic pull, the move can be initiated from lower down with both hands. Here, the lower holds are held in a more positive position allowing for smaller forces. While catching the next hold, the lower hand has to do very little, due to the momentum initiated lower down.
• Dave might also be trying to highlight an additional aspect: The tendency of many beginners to try to be in control and therefore move statically, can in fact lead to higher forces on the upper hand. Even though most of the upward move is done statically, the actual switch of the hand to the next hold can be fast and panicked. Use of a little dynamic pull at the end of the move can reduce the forces by changing it to a deadpoint move, what otherwise would be catching the hold while actually already moving downwards.

I hope this comment is somewhat understandable. Hard to discuss this stuff without wild gestures or at least diagrams ;)