Is FIU's spread offense legal?

Is FIU’s spread offense legal? Yesterday I went to Florida International University’s game against the Akron Zips in Akron. FIU runs a hurry-up spread offense set, which they ran very effectively.

I question how they did it though: the right guard would take his position next to the center, then the guard would look back between his legs at the quarterback - set up several yard deep in the backfield - then the quarterback would call signals, the guard would touch the center’s leg and then the center would snap the ball back to the QB. It seemed to me that the guard’s movement of his hand to touch the center was illegal motion or offsides, but no penalty was ever called. So what’s the story?

I believe as long as he doesn’t make a movement forward, and resets himself before the ball is hiked its legal.

It used to be offensive linemen couldn’t move at all on the line of scrimmage, but they allow them to make hand signals nowadays, even if they are “set”.