So you want to continue typing, but in an invisible field hidden by a different foreground app?

It's not what I would call invisible, but yeah that's the behaviour I would expect. That's also similar, to what already happens when I type in one window, while I scroll in another.

That's only possible when they are partially.side by side otherwise you wouldn't be able to hover over the background window

Or on top of each other, so yeah it would only work, if at least one of them is not maximized/fullscreened. (And none has holes in the right places, but I have yet to see a program, that makes an actual use of this.)