>> 0. emacs -Q
>> 1. C-h l
>>
>> Then point in the *Help* buffer should be at the bottom,
>> but when setting switch-to-buffer-preserve-window-point to nil
>> instead of using set-marker, point still is at the top of the buffer.
>
> I'm confused.  Here point in the *Help* buffer is always at bottom
> regardless of how 'switch-to-buffer-preserve-window-point' is set.

Dmitry reverted my patch in bug#35624 because of no progress here,
so I needed to implement this quickly.  It generalizes
help-window-point-marker to a more general variable useful
not only in the Help buffer but everywhere, and all my tests show
that it works well: