But... I don't remember it like that in SA on the PC at least. Weird. And I'm very sure III even had an option in the graphics settings to enable widescreen support, which was pretty odd. Why not just assume square pixels and figure it out from there...
SA on the PC and SA on the PS2 are very different beasts
The widescreen setting in the menu adjusts 3d rendering (and not even in the best way imaginable), a lot of other things are unaffected by it.