First of all, the video is wrong. The hijacker never identified himself as "D.B. Cooper". The ticket was bought as "Dan Cooper" and the news media got mixed up and reported the name of someone the police interviewed because of name similarity.
It's possible the later contacts were fake, and not the hijacker.
That being said, there's a good possibility it was this guy, and that's why the police sent his name to the FBI in the 70s. Lots fits.