Very interesting how you can definitely see 3 distinct groups emerge in recent years. I'm guessing linesmen are the majority of the group that really shifts over to the right.
What I find most interesting is that there's a clear gulf between the (probable) linemen on the far right and the others. That middle ground is probably not best suited for any role - if you're chasing the receivers, you're going to be too slow, and if you're trying to protect or attack the line, you're going to be too small.
Take a look at this reddit post with more detailed information that's position based. http://www.reddit.com/r/dataisbeautiful/comments/1oh47i/heig...
These players, while having some responsibility in the passing game are primarily involved in either running the ball, or defending against the run. And having a bit more mass there is very beneficial, but they still need to be able to have the speed to be able to work horizontal across the field and sometimes be quite a ways away from the line of scrimmage by the end of the play.
http://en.wikipedia.org/wiki/William_Perry_(American_footbal...
Tuinei was a contemporary with Perry in the mid-late 80's, but Allen wasn't drafted until the mid-90's.
I still say that Perry was an inspiration. :)
edit Fix team name. Ooops.