My first Mac was Mac Plus ... since then I am not
aware of any Mac that
couldn't use generic SCSI drives. I don't know what the Apple firmware did
(bug fixes?), but nothing was locked to it.
Sure there was... back in the Mac II days, the Apple formatter checked
for Apple drives in the copyright string (via IDENT packet, AFAIK).
The drivers were not Apple-drive specific, so there were 3rd-party
formatters that would get that industry-standard drive working with
your Mac.
I have multiple Seagate ST1480N drives. Most were out of Suns, but
one has an Apple sticker on the outside and says (in part) "(c) Apple"
when you query it.
That was the main good thing about the move away from SCSI, they also moved
away from this nonsense. The other good thing was cheaper drives.