? Curious. In this case, how is sleep 10s a safety feature?

The screensaver should never see keyboard input. And it shouldn't take 10s for the visual changeover - even for Windows.

Happy to read if you've got a pointer for me.

Sorry, misread.

I read it as: made an error while typing my password in screensaver mode, needed to wait 10s for the next try.

Waiting 10 s to be able to input your initial password is, I fully agree, not acceptable.. (And even not on Windows, which I try to avoid as much as possible, among other things, for those reasons. :-))