Can I ask a dumb question, here?
Why do I care (I'm guessing that I would, if I knew).
Is this just another Unity/Ubuntu thing, or is it more general problem?
All I've found is there's this option in compiz (newer versions only? I don't recall seeing it before, but I don't fiddle much with compiz settings anymore).
I'll be quite satisfied with a good link, to start my homework on.
Unredirect Fullscreen Windows:
Should programs be allowed to draw directly into a fullscreen window, bypassing the compositing process? This can significantly increase the performance of fullscreen games and videos, but may also cause visual glitches. If you don't know which setting is right for your use case, it's safer to leave this option disabled.