Well I wouldn't say it's just height and weight. It is, as you said, style as well. Certainly there are smaller guys who are tougher, and bigger guys who are more passive, but I don't think it's necessarily a strict question of toughness.
I think it's viewed more through the prism of having an undersized defense, the wear and tear that goes into playoff hockey, and trying to find more balance on the roster.
So I don't interpret it to mean they are going around with measuring tapes looking for bigger guys. I think they just want more balance --- same as they want with their forwards.
I mean obviously a guy like Lindholm isn't a giant, so it's not a matter of inherently moving skill for brawn. But having a smaller defense, regardless of the snarl, is something that would be a factor. There's no getting around it.
The same would be said if there were a bunch of forwards who were 6'2, 210 pounds and lacked certain speed or finesse attributes. It's more about the blend and the type of hockey that is played outside the regular season setting.