Originally Posted by
Kapusta
But I am NOT delivering the same power with just the down stroke (when running flats). I could not do so even If I wanted to.
It is a meaningless hypothetical.
Get off the saddle and you will, but you'll also tire faster, which is the least efficient way... Or put it in another way, your max down stroke power will tire your muscles more than the same power output using the whole pedal stroke so again, more efficient...