Not a mistake. At worse a tradeoff. Hiding a scroll bar when you go below some arbitrary document height that would classically warrant a scroll bar is just confusing. People who use a mouse to scroll will not know what to do and assume there is a bug. And sometimes you want scrollbar level control even on a short document.
It is not forcing them to use the scrollbar: keyboard shortcuts and menu items should still work as well.
> Hiding a scroll bar when you go below some arbitrary document height that would classically warrant a scroll bar is just confusing.
No it's not because you OPT INTO this feature and could change the document height from arbitrary to a threshold where using your wheel is uncomfortable (and that would depend on your device, e.g., with infinite Logitech scroll wheel that length is much bigger since it's very easy to scroll large distances)
> People who use a mouse to scroll will not know what to do and assume there is a bug.
No they won't because they'd OPT INTO this feature
> And sometimes you want scrollbar level control even on a short document
I never do, but then there are also solutions for this that don't involve some narrow understanding of the principle of least surprise
> It is not forcing them to use the scrollbar
But it is forcing them to clutter UI/waste space by not allowing to hide the scrollbar in most frequent use cases
Opt-in can solve that - only users that don't get surprised by a lack of useless elements can remove them