Yes, I've been confronted with it just yesterday.
Say you have several applications open at the same time.
Non of them is fullscreen.
Now suppose you have these window spread randomly around, but at some point they overlap.
Normal behaviour, when you click any app-window, is for the clicked window to grab focus, and be brought 'fully' to front, partly covering some other app windows.
Now suppose I print to PDF24, the PDF24 editor window pops up (at its previous location) but will not grab focus, so will not be in front.
It's even worse, even when I try to move it in front, it will not let me do so.
Instead, all I can do is move any other covering app-window aside..
Is my explanation more clear now?
Erwin