IIRC, The 14 books of MT are all based on Rambam's systematization of the 613 Mitzvos. Most chapters start with the list of the founding Mitzvos from which the rest of the Halochos follow. For example, Hilchos Mechirah:
"These laws contain five mitzvot: one positive mitzvah and four negative mitzvot. They are so and so..." Mechirah-Chapter-One
However, some don't, for example, "Hilchos Shecheinim", or the following "Hilchos Sheluchin veShuttafin":
"The purpose of these laws is to know the proper way to divide the land among partners, how one should remove factors that may cause danger to one's neighbor and those upon whom one's property borders, and the laws concerning the privileges granted to a person upon whose land one's property borders. These laws are explained in the chapters that follow." Shechenim-Chapter-One
From that introduction, we can deduce that he was aware of the fact that those chapters don't have Mitzvahs in them.
What does it mean that whole chapters don't have founding Mitzvos to rely on, and why did Rambam decide to make them separate chapters instead of a branch of other Mitzvos according to the basic logic of his work?