Glove side movement change-up?

Hey all. I’ve wondered for a while why all change-ups seem to get arm side movement and not glove side? Every instructional video I’ve seen talks about arm-side and never glove side movement. My son is learning to throw a 2-seam change-up with arm side run by pre-setting a bit of pronation. I just wonder why he cannot just sort of pre-set a bit of supination and throw it with a bit of glove side movement. Seems like it would be a good compliment for a cut fastball..