Every possible tiny variation is patentable
Jaz: disk in cartridge, motor, heads and controller in drive. REV: disk and motor in cartridge, heads and controller in drive. Pre-USB floppies: No intelligence in drive at all, just transistors to amplify control signals enough to drive stepper motors. The disk controller chip (on an add-in card, on the mother board or integrated into the chipset) had just enough brains to match the sector/track fields in the sector header. Everything else was handled by the CPU. Early hard disks connected in a similar way to floppies, with the controller (which could handle multiple drives) separate from the mechanism.
Drives gained intelligence because intelligence became cheaper, the market size increased giving economies of scale, and the reduced latency (between mechanism and controller) made a big difference to performance. For a while, it was often practical to swap the controller cards on a pair of similar drives. This became more difficult because the modern interconnect is more difficult to swap and drives are cheaper than the time required to fix them.
Where to place the divisions between media, mechanics, electronics and intelligence have always been selected by the market forces, not because only a single person on the entire planet had enough brains to spot that a component had become cheap enough to bundle with the medium. The market is going through another big shift: consumers are switching from mechanical to solid state and data centres are becoming the major/only customer that needs the huge capacity of modern drives.
It is about the right time to change which bit goes where again. Patent offices all over the world are calling this an invention worthy of protection - without any details of a standard interconnect or how to implement the standard. Patents were supposed to be about rewarding publishing research so that everyone else did not have to repeat the research. In real life, patents are a way to punish people who do research because a patent holder who contributed nothing can demand royalties from the people who do the actual work.