I beg to disagree that you should want to do the same.Once again, you are off topic. It’s not about buddies.
But for your sake, I asked him the same question about closing the valve and his answer was priceless: I am a Professionnal and I don’t want to scare the customers at the surface with my bubbles. This shows that he was completely in control. I wish I could do the same.
If you are on single cylinder, unless it’s closed shut or leaking extremely fast, just breathe from it and ascend. That’s a lot less risky than doing a cesa.