This art actually looks like it’s based on an Apple Extended Keyboard II. It’s been a really long time, but if I remember correctly, those had ADB ports for the mouse on both the right and left side of the keyboard (you could use either, or possible both for other ADB devices).
I agree with your take, but none of these games are as frustrating as Bayou Billy. I wonder if some dev at Konami just hated Americans?