Good points. I have no idea why they would do this. Its possible they did a triple layer but literally none of these scenarios make an sense at all. If he is on a green screen it is a hell of a lot of work to get it to match the perspective, angles, lighting, etc. It would be so much easier to just have him act out a presser and then paste in the mics. If so, then there is zero reason (except incompetence) to make a third layer of his arm.