Yeh, I thought it was unreasonable that the presenter said that it caused problems. The problems weren't with the separate contractors working together. As far as I could tell, there were no problems with the frames fitting on the basement. The problems were with the ordering and supplying of the windows. The second contractor would have made the same errors if he'd tackled the entire job, and who knows whether the first contractor would have had the same problems if the windows were his responsibility. Perhaps he would have run the entire job flawlessly, but that type of prefabricated framework was not his specialty, so he may have had a different set of errors to deal with.I thought that was a bit odd as well.
Good excuse to take a holiday anyway. :D