It's interesting, but it doesn't actually preclude the possibility of the Alone Branch leading to further branches, and that is something we won't know until next episode.
I personally think that the Alone Branch is going to lead to future branching, Quinn for example is looking to get MC involved in her drug dealing, Nicole wants to go on a (proper) date with him, Lily has been harassing MC to "roll" with her for several episodes at this point, Riona hints that she doesn't actually find the slut lifestyle all that fulfilling, Sarah and Mel are definitely a dead end, and fuckface has some interesting words for himself if he ends up in the bed with Tara, Gina, and Tiffani;
Also, if you make out with Riona at the party and you end your night with the three thots, or with the bunny thots, you get MC and Riona making out as your end screen, if you completely rejected Riona's advances you get a view of the rain and the brick wall as seen from the window in MC's room.
Then again we are talking about the dude who made Acting Lessons here, so it's not impossible that he's going to fuck you over for not picking one of the main girls.
(I always pick Melissa in AL BTW)
I remember reading in one of DPC's Q&A sessions (can't remember which year) where he wasn't cemented to specific endings for any character, and that he hated it when one of his favorite TV shows ended up forcing a really shitty ending because the writers had already decided on the ending when they first wrote the show, which then led to all the character development from between the first and last season being ignored, and that he would never do such a thing.
All in all, I don't think you should attach too much emphasis on the branch name during E9, consider the fact that he's introducing a cheating mechanic for all the main girls, which suggests that those branches won't be permanent either. I don't see why you would be able to get off an MG branch and onto the Alone branch without there being any possibility of the Alone branch also leading to further branches, take Josy as an example, it's pretty much made explicitly clear that you're going to get a Josy solo branch in the future, she looks overjoyed if you tell her that you're thinking of her all the time, because she's thinking of MC all the time.
I'm looking forward to E10, I think DPC will throw a curve ball at us, but I hope it's not a retarded curve ball.