That's not a bad description, I noticed in the Spence fight that he was using that old Archie Moore crossover defense. Also used by George Foreman. He is a student of the game. I think that Bomack introduced that to him.
A guy who fights yearly is not a throwback fighter. Yes, Bud has skills and could fight in most eras, but there is no evidence that he could keep up with the schedule necessary to find 5 or 6 times a year, or more. Bud has a unique style and makes the most of his long reach and sharp reflexes, but it is not an old school boxing style. In fact I'd be more inclined to say he has evolved to a style that is unique to Bud.