"A disk is a bunch of bits" doesn't seem to me like an accurate characterization of microcomputers at any time, really, in the last 50 years. I started to say that I think things got really complicated with SSDs, but spinning hard and floppy disks were never that simple either.
I don't mean to nitpick, and I'm no expert, but I think the non-bit-array nature of storage had a lot of implications for users doing low level stuff - for example, copy protection sometimes exploited the hardware to try to make an uncopyable disc. Or if you were setting up partitions on a hard drive, you'd need to know about more than just "disk = bits".
https://en.wikipedia.org/wiki/Cylinder-head-sector https://en.wikipedia.org/wiki/Logical_block_addressing https://en.wikipedia.org/wiki/Modified_frequency_modulation
"Commodore's Amiga used an unusual format which got closer to the disk's raw (unformatted) capacity by eliminating the gaps between sectors and simplifying the identification data. This meant that individual sectors could not be rewritten; the Amiga would simply rewrite the entire track."
https://en.wikipedia.org/wiki/Floppy_disk_format
I also remember that audio CDs, even though you could read them on a computer, were very, very much not bit arrays. Despite their vaunted "digital" nature, you couldn't rely on getting the same bitstream every time if you were ripping them to disk. https://en.wikipedia.org/wiki/Cdparanoia