I've always been under the impression that Rose was the only one who even had breasts. Every gem's torso except her's is shaped in a way that implies they have no breast and since breasts exist so mammal mothers can breastfeed and gems have no need for that, it makes sense for gems not to have breasts (making Rose the obvious odd one out). It makes me wonder if Pink Diamond originally based the design of Rose Quartzes on humans after coming to Earth. It also makes me wonder that if that's true, if that may be part of the reason Rose was more free thinking than most gems.

My personal headcanon is that Pink wanted Roses to be "Guardians of the Zoo", and based their design in what, after some study, looked more "protective" (AKA motherly) for them, and that's why they have a more human-like appearence and healing/defensive powers.
Also I think our Rose was the human who healed the zooman in that old legend about "hurt", and that moment caused her to like humanity and thus, start the rebelion.