Can you provide me with the details on which rounds he played these positions and how long he was on the field? Because the way you are presenting this information makes it sound like he was grinding in those positions week in and week out.
But to address your question, playing hooker and lock (in patches) evolves his understanding of those roles. When you are a half, the better you know those around you, the better you anticipate what to do and can make better choices.
Im not nitpicking, I'll discuss whatever you want.
Can you also share where its been quoted that he is putting on size to transition to lock? I believe that may have been one of the options on the cards (according to the forum) whilst luai was here and if Latu kept getting injuries - because in the best interest of any team, you cant build your team around a bloke who plays 12 games a season. But i never heard this from anyone of note.