As someone who has used in-ears a lot, his reason makes perfect sense. If you are trying to lock in a good, consistent mix, a singer moving along different parts of the stage like that would screw with things.
As to whether he has his own voice in his in-ears, he might, he might not. I know a lot of guys that don't actually mix their vocal into their in-ear mix because when you have ears in, sealing everything off, you can hear yourself singing in your head, even with a pretty loud band mix.