Not the author, but I no not understand the desire to use multiple apps. I am never going to want to carve one out as a separate module I re-use in another product. It is all interconnected, why add arbitrary boundaries separating them? Put everything into a "core" app and move on with life. Maybe if you are an enormous organization working on Instagram where you have rigid responsibilities per team.
So you’d prefer one file with all models? Do you break out into apps for business logic? Keep models in one app/file. Then domain driven design elsewhere?