It's pretty easy to see why this behavior can come from programs that's don't use any standard OS toolkits, but go for custom or cross-platform solutions:

- show the tooltip - rely on move events on the main window to hide it

the move events are usually received only when the window is visible (and focused depending on the os), unless you take extra measures to grab the pointer and/or listen on global events, which involves more trickery to work right.

It's the classic scenario where a decent system toolkit has this figured out and solved for you, while doing the same by hand looks somewhat easy and normally works 95% of the time, but fails in odd ways and drives your power users crazy.

Driving UIs heavily by keyboard and shortcut is the sure-way to hit that remaining 5% all the damn time nowdays...

Yeah, I imagined the same, but can't recall or reproduce in anything else now. Possibly a Mandela Effect?

I see it a lot with Windows Explorer and Microsoft Word, never with Firefox, even though I use all of them daily on my work laptop. It seems people have so different usage patterns that they see completely different bugs...

Altium Designer used to have the exact same issue for a very long time but I think it's finally gone some time ago

Finder does it to me all the time