I realize it may be comparing apples and oranges but in pretty much every other major sports his growth would be completely normal. In NFL, NHL, NBA etc. a kid gets drafted at around 19 while he is still a scrawny teenager and a few years later he finally fills out.
I'm not saying he doesn't take steroids because nobody knows for sure but I don't think its fair to blame a 22 year old for getting bigger. Lets not turn MMA into baseball or cycling and start assuming everyone who succeeds is cheating.
Also, Aldo and JBJ last 4 fights have been outside of Vegas and California...steroids? LOL