It probably isn't. Everyone's voice comes out more naturally when there's no additional muscle tension - as an experienced karaoke singer I've noticed that when I'm singing a song like BOR or Always and take the mic out of the stand, my whole body immediately relaxes as I start walking around and the high notes somehow become much easier to hit. In Jon's case it probably wouldn't help much, as his voice is so damaged that the high register has simply disappeared, but at least there would be some visual distraction from his vocal struggles if he was moving around more and therefor adding some energy into his performances.