I thought it was cool and done in a very respectful manner and so it honored John as well. Paul gets a pass on this because they were boyhood mates and that friendship preceded the legal, political and financial arenas they would eventually become immersed in later on. Also, since John asked Paul to be in the band and John says that he actually chose Paul to be his working partner then It feels as if Paul is lifting John up and saluting him with this tribute duet. I see nothing wrong with it and don’t think there was any suspect, underlying motives involved here. I could be naïve but I just got a feeling it was simply an old, nostalgic, maybe even cathartic, way for Paul to be able to jam with John one more time.