> it would still need lots of the other parts of Emacs, e.g. the buffer data structure
As I wrote right there, the embedding app could have its own implementation of low-level Org parts, talking to the app's internal structure and storage.
Running the whole of Emacs on a phone, and with tons of crosstalk to emulate the display, and with logic in the app to process that emulated display and convert into the actual interface, would be bonkers, which is why no one does that. Completely wrong level of abstraction—it's just the same problem of too much low-level fiddling, amplified into an entire inter-app API.
As I wrote right there, the embedding app could have its own implementation of low-level Org parts, talking to the app's internal structure and storage.
Running the whole of Emacs on a phone, and with tons of crosstalk to emulate the display, and with logic in the app to process that emulated display and convert into the actual interface, would be bonkers, which is why no one does that. Completely wrong level of abstraction—it's just the same problem of too much low-level fiddling, amplified into an entire inter-app API.