But most of those games that burn 100% CPU still burn 100% CPU even if the game is paused with a static pause screen and the container window is scrolled past t

But most of those games that burn 100% CPU still burn 100% CPU even if the game is paused with a static pause screen and the container window is scrolled past the flash area and the browser window doesn't have focus and is totally obscured. So it's obviously not a deliberate tradeoff.