I just watched the vid Carsten pointed out. Endo is not showing any technique here, but more the flexibility your have, the freedom of movement you still possess, when your feet do not move. It is what we work on to develop and I guess Carsten does too. Move feet only when necessary (when for example ma ai no longer matches what we are trying to achieve with the technique).
Perhaps this can convey a little the way we work...
Maybe that's one way to put it, so long as the point is not that the feet are not moving, but that something is not allowing the feet to move in space, then I'd agree. The only difference between a step, a kick, a punch, a headbutt, etc., is whether there is something in the way, and where that something in the way is. You have to sincerely try to take a step, just in the same direction as the force is going, that's how the force transmits to the ground, that's how the force transmits to the target. Otherwise it's like trying to hold a skyscraper up with chocolate pudding; chocolate pudding is nice on its own merits, but it is not a building material.