I mentioned him as a shutdown defender not because he was good at it. I mean I thought he was solid at certain parts, especially when it came to surviving forecheques and breaking the puck out of the defensive zone. I said that because of how Dyck used him during early parts of the season. When he started trusting in Bo more and become comfortable with his own game it started to explode offensively, I still very much think it was a tail of two seasons for him. Not sure what statistics there are out there for junior hockey, but I wouldn't be surprised if there was a large disparity between his points between the first three months of the Dub season compared to the final three months.
Once his offensive exploded, I saw him more of a Kris Letang type of defender where people overrated his defensive game simply because he had a "physical presence" out there. I agree he still has a lot of work to be done, one as you alluded to is just be more consistent in the defensive zone and honestly that comes with time and experience. With that said, if there is a part of his game which could regress it should be his offence where I think his stats are overblown compared to the actual amount of talent he has. That doesn't mean he sucks or anything, but I think he's more on the bottom-end of the elite spectrum when discussing talent than on the top end.
As for his lackadaisical play, I think a big part of it is when he started focusing on creating offence for his team. As the coach trusted him more, there was a distinct change in play where he kept the puck longer and went more for IDGAF rushes than what he did earlier by conducting smart out-zonal passes. Instead of focusing effort on the defensive side and making that lead to offence, he went sort of into his cocky nature of "I'll try to stickhandle it out of the zone and go on a Scott Niedermayer rush" which obviously doesn't work every time you do it. I am not trying to defend him here, but more of figuring what happened and why.