While it may be "commonly accepted" by those who have only a casual interest in the game (fans & media, for example), the way that we officiate line play may be of interest to you.It is commonly accepted that one could call holding on practically every play. So, as a rule, and since we've eliminated bias, one would expect calls of those type to even out over the course of a game/season since, afterall, holding and/or PI is enforced the same for either team. However, if a team is prohibitively stronger than its competition, you would expect those numbers to be skewed in favor of the stronger team.
As long as the blocker establishes and maintains his position in front of the "blockee", we don't worry about whether or not he has some jersey in his hands. He has legally obstructed his opponent. This is what we see on the majority of plays
If the blockee moves to go around, the blocker must now either move his feet to maintain that position, or let go of the jersey. If he fails to let go, or if his hands are outside the frame of the blockee's body, you may see a flag for holding.
Naturally, this is a simplified version of the guidelines we use. There are other specific acts that will draw a flag, and sometimes an "obvious" hold away from the point of attack is passed over, with a verbal warning to the offender to "watch your hands, #78."
It's interesting to me that many times a team who blows out its opponent is penalized for more yards than the losing team. (If you don't believe me, look in the box scores in any Saturday or Sunday morning paper.) Why is this?
In a blowout game, the team who is leading often puts in second or third team players to get them some game experience. These players haven't gotten as many "reps" during practice, and (especially at the HS level) may not be as athletically gifted as the starters. As a result, they tend to draw more flags than the losing team, who may have kept their starters in for the entire game. In addition, the officials will often "pass" on throwing flags for non-safety related fouls (especially against the losing team) that only delay the inevitable conclusion of the game.
Therefore, a team's penalty stats may be misleading. LSU was the most penalized team in the SEC, yet they're playing for the National Championship. Alabama was among the least penalized, and they finished 6-6. How do you factor that?