[Tublecane]

“I don’t think I could agree with that. The O line is many times more complicated than the D line”

That may be so. However, “skill positions” are traditionally limited to backs and receivers because they are the ones who move the ball forward. Lineman can be eligible receivers, but not very often.

[MarineBrat]

The O line has dozens of plays, schemes and responsibilities for recognizing shifting defenses, and those plays have shifting assignments depending on what the defense is doing. The minds of the O linemen are in lockstep when they're set at the line. The minds of defensive linemen are for the most part thinking .... "BOING." Which, loosely translated means, "I'm gonna git that sucka!" :)

O linemen are economics majors. D linemen are liberal arts. :)