It is true...
There can be no new material for concerts UNLESS it is recorded and then played back. However, if Steve's voice IS shot, then the new recorded vocals will not be in synch with the old recordings. Unless he really sings the entire concert and his vocal quality doesn't change.
So, I suppose the set list COULD be a telling sign, either way. If they stick to the same old songs, it makes sense. If they do new material and his voice sounds different on just those songs, then there ya have it.