RozenKristalMy thought was that SA is taller, AND it is flat across the top. Presumably easier for them to work with when making the key cap. You'll also be able to see what's going on inside the key cap better without weird optics possibly happening because of the profile being curved on top.
If you use it as an ESC key, why worry if the profile is an exact match? I'm fine with the keycap standing out, and I want Mt. Fuji to look its best!