I recall Belichick talking about this and the change is primarily due to the evolution of the college game, which also made guys with that body type more rare since big bodied players who are athletic are so few and far between. So there are fewer of those guys coming out that can play at the NFL level. That was one of the things that made Hightower so unique. I think a lot of people forget just how good he really was.
And agree on the fact they're trying to get bigger and stronger on offense. There were a lot of short-yardage situations last year they failed to convert, and the fact they couldn't get one-yard when they needed it on the ground was frustrating. Hopefully some of the changes we've seen this offseason will help, because they'll need to be better about that this season.