I won't link to an unauthorized recording, but I saw another link of the same incident from a much closer angle that (I believe) sheds a bit of light.
Some of what I'll consider "hard facts":
-JLB has a backing track on the main vocal parts of some songs - that much is obvious from what I've seen so far, having now multiple data points from multiple songs on multiple nights.
-James is always singing, whether there is a backing track or not. And you can often hear both James and the supporting track in the background if you listen closely
-In the alleged "lip sync" performance, from different angles you can see James trying to communicate to the mixing board guy that he needs more volume
OK, now this part is more subjective and the matter of my interpretation, based on other angles of the incident I saw:
- Despite James' hand cues, the mixing guy does not seem to make any adjustments; either that or James' mic has failed
- Seconds after making the hand gestures, James seems to realize that his mic is not live
- He turns away from the audience, in my mind, he is trying to avoid what it will look like if he's seen belting the song with no "live vocal" audible in the mix while a backing track plays
- Conclusion: James is not "lip syncing", at least not intentionally, but it seems that way because the live mix has failed and the backing track is still going, maybe a miscommunication, maybe a technical error, who knows. Either way, I don't think it's intentional to have James be lower than the backing vocal. I think perhaps the levels of the vocals in relations to one another are what I would consider to be part of the live show that has not been ironed out and I'd be shocked if we're seeing this still after a few more dates.
My take? I'd be fine with no backing vocal. But that's just me. I have reasonable expectations for these guys, especially a singer of this caliber, and I can hang with the idea that a performance might not be perfect. I find it a bit unfortunate that the band have been using canned backing vocals for awhile now, but I guess someone who knows more than I do has already determined that fans like me are lesser in number than those who show up expecting perfection.