As you can add different audio tracks you can also add multi video streams and that's called multi angle. But the specifics of the streams have to be the same (same length, same GOPs, etc). You don't have to have multi angle for the entire movie, you can do it for certain chapters if you want.
Seamless branching is different from multi angle because you can basically make a playlist of chapters and play them in any order you want (so no same size, Same GOPs etc.). But to make a playlist play seamless you have to order the info in such a way it plays seamless. And that's difficult. But I've been playing around with it and I think I can make almost any playlist play seamless, jumping gaps of multiple gigabytes. It's not true seamless branching offcourse, it's semi seamless branching but it plays seamless. I have to do more testing, but it would be so cool if you could for instance in the dvd menu choose between an all digital Battle of Yavin or an all original models Battle of Yavin.