OK, it may not have been the most elegant of processes, but let's give the R credit for being current with the rules. AR 3-5-2-V was changed for 2025 to make this first occurrence an immediate Delay of Game foul on Team A for snapping the ball before the substitution process is completed. (Previously, this was "No foul," on the first occurrence.) With the 'iron cross,' the R was successful in notifying the world that the 'substitution process' was now in progress, and the ball was not to be snapped until the team is released to do so. Even the H uses the iron cross. The AR is very clear that, if the officials can't prevent the snap, the ball remains dead, and a DOG on Team A results.
Mechanically, could things have been better? Undoubtedly. The C was miles behind the NZ, and didn't appear to even attempt to get to the ball. The U wasn't exactly close, but, with some hustle, he could have got to the snapper, had he begun the instant the sub came off the sideline. Lacking either of those two things happening, the R did what he could do by stepping in front of the punter. I don't fault him for stepping away from being in a direct line. Perhaps he could have stayed slightly forward of the punter, in his vision, to keep him from calling for the snap.
But, the period of time for Team B to BEGIN a substitution started when the sub got into position on the line (not when he stepped on the field), and that period of time had only just started as the R began to move back. At that moment, the R was still in the 'iron cross,' and Team B had 3 seconds from then to BEGIN a substitution. The ball was snapped immediately, far before the expiration of Team B's time period for beginning a substitution. That's a foul (for 2025). It would have been wrong to have allowed the play to happen.
All this garbage about, "How is the snapper supposed to know..." yada, yada, yada. Talk to the coach that didn't get the players on the field in a timely manner. Where is the criticism of that guy?
Let's place the blame where it belongs, and that is on Team A, for failing to have their players on the field in time. They broke the rule, and got penalized.
The play clock was at 6 when the ball was snapped, and the 3-second window had only just begun. LSU could have waited 2-more seconds to begin, then easily have taken 4 more seconds to get a player in place on defense, and SC would still have gotten a DOG foul.
Everybody (in the media and SC fans) can stop whining now, and move on.
Kudos to the R for making the call. Next time, though, use S21, and announce, "Delay of game, offense; snapping the ball before the substitution process had been completed; that's a 5-yard penalty - 4th down." And further kudos to the R for having the game clock start on the snap for the next down (by rule, after a DOG from a scrimmage kick formation). I have no problem with the officiating.