I don’t know that we are saying separate things. COG speed over ground is a function of the two aforementioned components. Changes in their respective values explains pretty much all locomotion, even most jumping events (Greatly increased forces generated before ground contact in comparison to sprinting, but with that increase in force comes a slightly reduced efficiency in storing the mechanical energy created, increasing ground contact time. But the force occurring before ground contact is increased to greater degree, causing more total force to be stored as mechanical energy, increasing the distance the athlete moves as a result of that action in comparison to sprinting. ) There may be some small force occuring after ground contact, at least outside of a treadmill, but to the extent this is a significant component of sprinting outside of the acceleration phase, where things are more mixed, it is correlated almost entirely with the force generated before footstrike. My understanding is that Weyland would disagree that any force occurs after ground contact, but I have seen studies that differ. Even in studies that suggest that it is occurring, it unlikely to be very significant and shows a significantly smaller EMG. And, again, it is correlated closely enough with pre ground contact force that they should probably be considered as part of the same action. EMG during the two periods show increases during fatigue while EMG during initial ground contact typically shows decreases and an increase in latency. Other factors that cause their individual values to change seem to occur in tandem as well and suggest that any force that occurs after ground contact is a continuation of the pre-ground contact phase of sprinting. They are very interesting studies, I forget the author off hand, but I can probably look them up if you would like.
Mechanics of the sprinter are important, but again, those specific mechanics as they relate to COG speed over ground are inseparable from force generation before ground contact and ground contact time, either increasing or decreasing them. (That there are two interdependent variables is the reason sprinters can show idiosynchrasies in running style and still show similar top speeds.) Let me know if you agree. I don’t think we are saying anything too far apart, but I could be wrong.