Yes, I've said that all aong that Bono was singing along a vocal backing track.
And yes, the musical backing tracks are more understandable for when they don't have enough people or the instruments to reproduce it with just the 4 of them.
It's like the "choir" type vocal backing track during Beautiful Day is fine, as there is no way Bono could reproduce that type of sound with his voice. But for them to use a backing track for a hard to sing part of a song is like the Edge using a backing track for a hard guitar solo that he just couldn't play. Both of those wouldn't seem right to me.