Some of it's genetic, I reckon, since my calves are almost identical to my late mother's, in shape and size, and she never lifted a weight nor did a standing calf raise in her life; I can get away with just stepping and they never alter, not really.
I did lots of calf raises when I was a teen but I'm not sure they made that much difference, though, at the time, it certainly felt that way...as did the 100 bodyweight squats per night which seemed to really solidfy the thigh muscles. I still reckon, however, that most calf size is genetic.
Arnie, from what I recall reading, had dinky calves in his youth and they only really started to fill-out and grow as he got older even his pictures are proof of that.
There is talk about toes-in during calf raises but MRI scans show that they don't really target the muscles half as well as the normal forward toes stance.
36.5 kg /80.3 lb Middle-Finger DL (right hand)...