Mintz may have described himself in that way, and I can also see him providing the FBI with information on John and Yoko.
If you read Michael Gregg Michaud's biography of Sal Mineo, you'll see how Mintz had developed a pattern of taking Mineo to Hollywood Italian restaurants, enjoying lavish feasts, and then guilting the restaurants' servers and owners into not charging the "great" Mineo for the meals. Mintz was another con-man. He was Yoko's Yoko.