It's not a loop hole. You can't be moving towards the LOS at the snap. It's been that way since there has been football in this country. It's illegal motion. If you do move towards the line you have to stop and become set before the snap.
What it is, is the league manipulating outcomes in games. Clearly the refs have been told to ignore this, and they are. They will until there is an uproar about it when someone goes full CFL motion in a playoff game and it goes uncalled. At that point they will make some sort of BS statement about how it's been a rule all along, then the following week they'll call the hell out of it to prove their point.