It's kind of hard to tell since he's a dark colored betta (very handsome btw!), but I didn't see any sign of fin rot or redness in that video. I would say he either torn his fins like you said or he may be a finbiter. I have 2 former biters (for the most part at least) & when they actively bite their fins start to look like that. Based on what I see, I wouldn't worry about fin rot.