Grigri question

First I want to make it clear that there is ALWAYS a hand on the break strand at ALL TIMES.

My belay partner got in trouble last night by a staff member at our gym.

I was projecting something on top rope. I was taking a break and just hanging on the rope. My partner uses a grigri and had his right hand holding the break strand in the down position. He moved his left hand under his right and grabbed the break strand with both hands (I'm still taking a break, just hanging during this). He then let go with his right hand so that just his left hand was holding the break strand in the down position.

He only does this if I am taking a break. If I start climbing he puts his right hand back on the break strand so that both hands are holding the break strand and then lets go with the left so that just the right hand is holding the break strand down and resumes the usual belaying position.

The way the staff member interacted with my partner made it seem like this was seriously putting me in danger.

My partner and I don't understand why this is so unsafe while the climber is just resting on the rope (not actively climbing), since the break strand is always being held and is always in the break position (being held down).

If it's truly dangerous, I would like to know. And if so, can someone explain why?