The only problem I think I see with that explanation is that conventional bindings don't "push down on the back side", at least not relative to the heelside edge of the board; all of the forces applied to the snowboard through the binding itself are inboard (between the board edges) since the binding baseplate is smaller than the board surface to which it is mounted. Hence, conventional bindings generally have the same basic, simplified force diagram you showed (though with additional inconsequential forces caused by rigid side supports).
Sorry, yeah I should have explained that better:
When you lean back in a conventional binding, the heel loop is connected directly to the baseplate. So, when the back of the boot pushes against the highback, the highback leans back onto the fixed heel loop and makes leverage in that direction. This way there are 2 main force vectors: a down-and-back force from the heel loop and an upward force from the boot under the straps.
On a Flow binding, the heel loop is a part of the highback and is not fixed to the baseplate, because the cable is what stops the highback from rotating backward. The highback does not rest against the heel loop. So, when the back of the boot pushes against the highback, the highback pulls the cable backward in a similar overall direction to the boot pulling back against the straps. This gives it 1 main force vector.
So what I'm saying is that with conventional bindings, force is divided into 2 main directions when leaning back vs. combined into 1 main direction with a Flow binding.
I didn't include the straps in my last explanation because I was only comparing the differences, and the straps are pretty much in the same position on both, but here it made it easier to explain. Also, there are other forces involved such as the heel of the boot pushing down on the back end of the binding, but again that is something that both bindings have in common so I didn't see any point in including them.
In actual performance, though, the difference in the force directions would hardly be felt as this is only a slight difference. So it doesn't really matter. I just wanted to prove that their "energy transfer from hiback to baseplate" thing would hardly make a difference.
If you did notice more powerful heel-edge transition, pulling back on the cable and straps with one single direction of force would be just as responsive than as dividing it into 2 different directions of force, depending on how tight the cable is (more forward lean = tighter cable = more responsive, which is actually like on regular bindings.)
In other words,
a. the Flow bindings might have more forward-lean, with or without adjustment.
b. you might not be feeling more power when transitioning heel-side because in the end, you're still leaning with the same amount of force but in different directions. Therefore, you could just be feeling the same amount of power but in a different way.
Anyone got any other binding suggestions for this guy? After all, that is what we're here for!