In my opinion this video should of never been released and I'm not surprised Nadal doesn't want to give credit. I'm sure he's pretty ****ed about it.
There are good things to be taken and learned from that video such as that even pro's work on very simple and what some might think are basic things. However, that video should of never been made public.
Throughout your life advance daily, becoming more skillful than yesterday, more skillful than today. This is never-ending. - Hagakure