Interresting theory. I was thinking along those lines as well. Even though, I was thinking that maybe Yama-jii took more time to control his zanpakutoh. After all he's one of the older shinigami and he's the one who founded the Academy . So he had no one to guide him...
However, what doe it means for Yachiru? She's got her zanpakutoh and all but she's not that mature yet. Her case is probably similar to HItsugaya then