Strictly traditional. At LICH, the housestaff wore the short coat, and the chief residents, fellows, and attending got the long coat as their reward for "time served".
An attending here at Duke told the story - just 20 years ago, when he was a student, the students wore short coat and street clothes. The house staff wore short coat and white pants; I think the white shirts was also indicated. There was a special Duke-only button-up front scrub top that was also worn (specially made for, and only for, Duke). The fellows and attendings wore the long coat. This way, in a moment, you knew who everyone was. Today, the short coat is for all students and interns, and general surgery is a special case - short coat and white pants for first AND second years.
As far as surgery here, besides people that are not white males, there is NOTHING different about surgery from 60 years ago. As traditional as the day is long.