Well, the writers claim that the branching off of a new universe is consistent with multivese theory...and it is....and multiverse theory also states there are already pre-existing universes independent of our own.
Therefore the line alternate reality from the movie can be interpreted 3 ways,
1. The time line of the prime universe has been altered.
2. Nero's actions have created an alternate universe.
3. The time line of an independent universe has been altered.
2. is the only one supported by writer statements. 1. has nothing to do with branching and thus shouldn't be in the list based on the writer statements about branching which you mentioned.