dave? not good.

ex-Navy acquaintance that even ships with a horizontal
prop shaft still have prop walk

end-plate effect

Chapman's explanation here uses the incline of the prop shaft relative
to the flow of water past the blades.

"asymetrical thrust" it is called, though Chapmans does not use the term

the inclined shaft and the HORIZONTAL flow of water
past the prop

doesn't have to horizontal, just has to different from the axis of the prop.

caused by the (forward) motion of the boat through the
water.

doesn't have to be from boat movement, just has to be water movement.

As the boat is jammed against the dock and not able to move through the
water there will be no horizontal flow of water due to forward motion.

no, the hull of the boat causes the water flow behind of the forward pushing
prop to "line up" not in line with the prop shaft, thus asym thrust.

The only flow past the prop will therefore probably be a flow parallel
to the shaft

no, the hul gets in the way, at least if the hull is anywhere near the prop

the water leaving the ascending blade (on the
port side of the boat) may produce more push on the port side of the
hull than does the water swirling down from the descending blade

why is this? what has "swirling" to do with it?

I have even heard the explanation that since the water is more dense at
the bottom of the rotation than at the top,

nah, the difference is virtually nothing. There is less than 1/2 psi pressure
difference per foot of water depth and water compresses
soooooooooooooooooooooooooooooo little than even several thousand psi wouldn't
make any difference.