You're right. But that really worked. Tony was very satisfied with himself (just as much as when he toasted to a job well done with Tony B. and Christopher). He has that set to his shoulders while his figure gradually shrinks into the distance as the credits roll.
Maybe the director of last night's episode wanted to try some new things.
Maybe they don't want to identify as high-brow or arty, but would prefer to have the trappings of a plain old TV show.
I think it was a direct homage to the closing credits of Silence of the Lambs, where Hannibal Lecter does exactly the same thing.
Very foreboding symbolism too, if that's what the director was going for. Like Lecter, evil Tony is out of the box, turning his repressed anger outward, destroying everybody around him and feeling very very good about it.