I havent seen enough of his games to have a strong opinion of his defense and defensive potential, but if Madden is actually considering him at 3 then I am pretty confident his defense projects pretty well in the NHL. I hear he has great straight line speed, great size, great physicality and is a beast around the net. Those are great tools to build from. Edge work and backwards skating is certainly something you can improve if your training is heavily focused on it. I would also add that fans tend to think they have a really good understanding where everyone goes and every year there are guys that drop in a big way or rise in a big way, indicating the fans views are not always the GM views. Just because mock drafts have him going closer to 10 doesnt mean that we can trade back to 10 and get him there.
I will try to watch more shift by shifts and get back to you on my thoughts, but at the end of the day a couple of games is still a very limited indicator of where these kids will be 10 years from now compared to everything a scouting department is doing.