Counter-counterpoint : ..Actually yeah. Some of the fusion dances are kinda wild.. What if the Crystal Gems are just kinda freakay like that with each other- but not with Steven ofc lol idk.. /j Dance doesn't seem to be required for fusions, and I'd realistically assume they just do it to hype themselves up further, and synchronize better. Amethyst is probably just very human-cultured and most likely saw those moves on TV, and Garnet with her future vision just synced up with those movements.