it's a little difficult to tell...I don't know if I'd suspect that if it wasn't suggested (the power of suggestion)...but...there does seem to be a slight change in 'audio' quality on he choruses...
I don't see any evidence of it in this video at all. Maybe you're thinking it sounds stronger during the chorus, but that's because the two harmony vocals come in. I think he sounds great here, even though I don't care for the song at all.
I'm going to see his stripped down acoustic show on Dec 3rd. I'll let you know how he sounds. I think it's just hi and a guitar, so obviously no lip syncing.
there is just something about the chorus that sounds too perfect and how his mouth is moving doesn't seem appropriate for the way he's singing, I dunno if he isn't lip-syncing I'm not gonna argue, this was just what I got from watching it