Why wouldn't he inject oil in the "bad" part of his calves then as well? 
May not be that interesting but some muscles don't "take" oil well or it looks too obvious. Some always say "why does he put Synthol in his already great arms but not his shitty calves?!" Well, you can hide some degree of oil in already well developed part without it becoming too obvious immediately and small muscles like calves or the very rear part of the delt may immediately show disfiguration
I imagine the soleus part of the calves might be hard to do. I don't know if anyone attempted to oil up hamstrings, actually I'm sure some have tried, and actually I've seen mention of some putting oil in their abs. Also heard claims of some pros putting oil in their forearms; heard this from a friend, who was training in Venice and claimed to know, about a certain pro about 25 years ago
You'd think injections might damage nerves in some parts but I doubt that's the reason we're seeing so many of these calf atrophies.
