I don't know what it slows down. DPC is mostly waiting on the animations I'm just saying give us the Halloween part of it if all of that is finish. Then While the those animations finish he can get started on 10 then when the rest of 9 is done add the rest to it and go back to 10. Just a idea and maybe people wouldn't like it
For some reason, I feel like it's just not that simple. I think development is more like filming a movie or tv show. Things aren't necessarily filmed and edited, shot-for-shot in succession according to the story line/timeline of the plot. Those last few animations could be for something in the beginning of the chapter, a nice "Friendsgiving" special (lol) for the end of the chapter because DPC thought "I know I'm already going to miss Halloween so might as well add even MOOOARRR", or for all we know those last animations could actually be for the Halloween party.
I could be wrong about it, especially if it's already been more or less confirmed that he's done with everything relating to the Halloween party but I still just don't think it's that cut-and-dry.