The docstring for the mentioned variable is unclear in that it does not
really tell what kind of scrolling (horizontal) is enabled and
incomplete because setting it enables horizontal scrolling and that’s
not mentioned (or, maybe tilt scrolling means that but that’s probably
an obscure term for many).

A patch is attached which is proposed as a tentative improvement. If
it’s good enough to apply, I do have my copyright assingment paperwork
done so it can be committed right away.