In NCAA football, only a BACK may legally be in motion at the snap. So, what is a 'back'? He is a player that is not a lineman, as defined, AND his head/shoulder is not breaking a line drawn through the waist of the nearest Team A lineman. Bottom line: if he isn't truly a back, by definition, he can't be in motion at the snap.
Technically, a player could be positioned such that he is neither a lineman nor a back. 1) He ain't eligible. 2) If he begins moving and fails to come to a complete stop in the backfield before the snap, he will commit an illegal motion foul.
If a lineman comes off the line and doesn't come to a complete stop in the backfield, he is not a back, and will commit an illegal motion foul if he continues moving, and is moving at the snap., even if he is well into the backfield.
As others have mentioned, we try to make all players legal, whenever possible and practical. If we can clearly tell he is offset from a player who IS on the line, then we call him a back (even if he may not be, by pure definition). Firstly, we need to check formations as early in the game as possible, and work to get these guys clearly legal - truly on the line or in the backfield - so we don't have a problem as the game goes on. Thankfully, the NCAA has included a Point of Emphasis for 2024, for players to get themselves legal. If you are supposed to be on the line - get up on the line. If you are supposed to be in the backfield - get in the backfield. You'll get a warning, but then we'll make the call until you have that epiphany of - "Gee, I guess they are serious."
The problems are that, not only do coaches teach their players to 'fudge,' but they don't read the book, and will have no idea about the Point of Emphasis. I can hear it now: "You're being too technical." Or, "When did they change that rule?"
Ignore 'em, and do the job we're there to do.
