Let me help you out here. a rudder has NO effect on which way a boat is
going
in reserve because of the prop. None. Nada. Zip. Zero. Nothing.

That's a fact of physics, schlackoff. get used to it.

Your premise is wrong.

As the vessel goes in reverse, water presses against the face of the rudder if
it is turned to port or starboard. The greater the speed, the more the water
force on the rudder. At sufficient speed, the force of the water against the
rudder overcomes the prop walk and the boat will follow the rudder, not the
prop.

When speed is reduced, the vessel will reach a point where the prop walk force
is greater than the rudder force and the rudder will not be useful to steering.

It could be argued that at sternway at all, there is some effect from the
rudder. It may not be enough to overcome the prop walk at the slowest speeds,
but in principle the prop walk is finitely reduced
with even the slightest pressure against an opposing rudder.

The water hitting the rudder is not being pulled over the rudder by the prop,
any more than the bow wake is created by water being pulled against the bow
when going forward. I think everybody agrees on that. But to say a rudder as NO
effect on a boat going in reverse because of prop walk is not correct. The
rudder exerts increasing influence as speed increases.

This may not be true for boats with itsy bitsy rudders, btw. It might not be
possible to get enough water pressure on an 8 1/2 X 11" rudder to offset prop
walk. :-)