Mac convert, another focus oddity

Try this with your Mac:

Fire up any application and have a window that has a scroll bar.

Then using Expose, switch to any other window that's smaller than the first window, so that at least part of the first window can be seen. Then move your mouse cursor on top of the first window (i.e the one that doesn't have focus), and try scrolling. The scrolling would work - even though the application itself is not in focus. It's as if scroll event uses "focus-follows-mouse" principle. Confusing? Hell, yeah. However, I'd still call this useful. If only I can type as well...