Honestly, much as recent trends have smaller players proving to be NHL able more than say, a decade ago, size is still a preference in drafting over lack of size.
In most basic terms, a Middleton Clone at 5'11 is and always will be less than the 6'6 version.
If there's a 6'6 D-man with an already established high ceiling skill set, then he goes in the 1st round. No such player ever exists in the 4th round.
Any team at any level looking to contend for a championship needs for someone on the back end with top-end size and strength, who can defend well. You could win without one, but you're more likely to win with one. If that player can score, then he's Chara. If not, just as a strong stay at home, he wins you games.
So, to my mind, the Leafs took three lottery draws on big defence-men in the later rounds this year. No player of this size with established superior skill was or ever will be on the board there, .... unless they are buried so deep in the nowhere lands of Bangledesh that it has everyone's head spinning.
If the Leafs can develop just one of them into a strong stay at home guy, then we win big time. If one of em does that and can score.... well ... but that's more the outlier than anything. Just, if the player had already shown that potential, they wouldn't be on the board at #101.
Though honestly, if the Leafs had just 5 picks in the draft, and burned a couple of em on this kind of pick, i would be more frustrated. It is though, a good thing to have in the system, and with the versatility that extra picks provides, i don't mind it. None of these three guys are true goons. They've all got different strengths and weaknesses, but are all hockey players.
For my money, Mattinen excites me most of the three, but we'll all have a better educated opinion on the matter come the new year.