He played hooker, but didn't he say it was only a few times.
Maybe it really wasn't working out.
These days, I think learning to scrummage at 2 isn't a problem. There's not a lot of hooking going on. It's pretty much bind, crouch, drive.
However, being a top level lineout thrower isn't so easy.
If he didn't play much at 2 in his youth years, he won't have practiced much throwing.
He clearly doesn't want to be a hooker.
It sounds like he still wants to be an occasional centre, but is happy with back row.