I've been trying to think of what might be the cause but I have no clue, except for the added physics accuracy in the latest version. If it was only rendering by CPU you would certainly see a difference when running at really low resolution. You can try that to see if you notice a difference, like, running it in a window at 640x360 resolution or something like that.
-screen-fullscreen 0 -screen-width 640 -screen-height 360
Still, it's weird that it runs lower than 1 fps...Even the added physics accuracy shouldn't make such a difference.