Speaking for myself I've never booked studio time and not had anything ready to go. Even now that I record my own shyt, I don't piece it together during the session.
That being said, the process for them Flint rappers would be completely different anyway from what Lupe was doing, they're making uptempo street/commercial type shyt where the main draw is the energy, flow, adlibs, etc. If you're just talking shyt the whole track then yeah that process is better for that, especially if you're lit af and you get the reactions from folks in real time if its hitting or not. It's still crafted but the listener reaction they're looking for is different from what a rapper like Lupe is typically looking for.
Great post. Are you from Oakland?