Doug Otte wrote:
In retrospect, do these discs even have branching? Is an alternate angle still branching?
Good question, and I can't answer it, but I can ask another one:
"Is there a (technical) difference?" Maybe branches are actually different angles?
No, there is definitely a technical difference between the two. You can have branching without angles, and you can have angles without branching.
That said, from what I can discern of poking at the disc structure, TOS uses both; it has separate playlist files for Enhanced and Original Effects, and chooses based on your selection in the menu.