Originally posted by deanallison:[..]
That’s a theory but without any proof that’s all it is, it isn’t a reason but merely your belief and I don’t think it’s a very good theory at that. The band could have easily worked on things whether the Raleigh show happened or not, in fact the show could have been a good rehearsal in itself if they were really placing that much emphasis on the New York shows.

It's not a theory I read it in this book "U2 live" which is very factual and documents every tour up to Elevation apparently the band and crew had copies of it and used it to look back and remind themselves of past shows.