I thought I knew the rules of American NFL football but maybe this is a nuanced rule regarding false starts.
I know everyone on the offense needs to be set for 1 second/1 count before snapping. However, there are several instances in recent games where I see everyone on the offensive line appear to be set and motionless, then they turn around to hear the audible from the QB and/or pass signals along to other teammates and no false start is called.
I've also seen where the O-line is set and motionless but then the defense shifts late to show blitz and people on the O-line start pointing out the new blocking assignments; again, not getting penalized for a false start.
Then we have an example of a "typical" false start penalty where everyone is set and motionless, the QB is still barking signals but someone on the O-line then rocks back 1/2 an inch and gets flagged.
So now I'm curious why O-linemen seemingly set are allowed at times to turn around to clarify signals and not get penalized but other times those same O-linemen are set and motionless get penalized for the slightest movement? Am I missing something that's happening at the field level that the TV broadcast doesn't capture and show to viewers at home?