I think there is an easier way to explain it (although I concede that if it were so easy, everyone would have accepted it by now!).
Basically, for a bit to have any leverage action, the reins have to be attached below the plane of the mouthpiece in the mouth. So in a bit that has a shank below the mouthpiece, it’s obvious how the leverage works: the cheekpiece of the bridle holds the bit in place (anchors it against the poll), while the reins pull the bit towards the rider which effectively pulls the bit onto the tongue and lower jaw. In a curb or pelham or Kimberwick, that action also tightens the curb strap or chain underneath the jaw.
An Uxeter Kimberwick has rein-slots that allow you to position the reins either in a “neutral” (i.e., on the same plane as the mouthpiece) position or in a position below the mouthpiece (a leverage position), plus the curb chain action.
A Myler bit with rein hooks allows you to use some leverage even with what looks like a straightforward, non-leverage snaffle bit because you’re attaching the reins below the mouthpiece’s plane.
The reins when attached to a Baucher bit are on the same plane as the mouthpiece. There simply cannot be any leverage. I don’t know if Myler makes a Baucher with rein hooks, but if they do, that could provide some leverage, but only because of the hooks. And of course there’s no curb chain involved. (If you added rein hooks and a curb chain, you’d effectively have an Uxeter Kimberwick).
