Every "Great" offensive defenseman has had a good partner that allows them to play their and not worry so much about the defensive side, They have each others backs and know their "Game".
Karlsson had Methot
Q. Hughes had Schenn and now Hronek
Makar has Toews
Hamilton had his career year in part to the fact that Grave's covered for him.
Hutson having someone who can cover him doesn't mean he stops learning. it just means that his mistakes don't have terrible consequences.
Your first sentence is pretty much the point I'm making. If Hutson's main issue is his defensive side, then he should be and needs to be worried about his defensive side. So it doesn't really make sense saying he needs to have a partner that will make him not worry about his defensive side.
Having a good partner such as Methot for Karlsson is nice to have if the goal is to win games and maximize your players' talents and on ice results. But I think Montreal is more focused on developing their players rather than winning games.
As a Canucks fan, I've read a lot about Hutson in college last season because Willander was on the team. A lot of the reports mentioned concerns about Hutson's game and hyper-rover style of play translating to the NHL. So far, it sounds like Hutson needs to adjust his game if he wants to stick in the NHL and I don't see how having a babysitter for him is mandatory in achieving that.
Hughes improved defensively not because he was babysat by Tanev or Schenn but because he made a conscious effort to work on his game every year. Schenn and Tanev were definitely helpful in covering Hughes' weaknesses but that mainly impacted on ice results rather than Hughes' actual development.
Obviously making too many mistakes that end up in the back of the net could negatively effect Hutson's confidence where he might feel overwhelmed and start playing too scared. But again, that's something coaching and Hutson's own perseverance can help with. Having a babysitter isn't mandatory for that either.