The term "disc" for storage predates optical media. "Disc" was the common spelling for a disk (like a floppy disk) on British 8-bit computers like Amstrad CPC or Sinclair Spectrum.[1][2]

It seems like the distinction simply comes from British and American preferences.[3]

I have no idea how Apple jumped to such an arbitrary conclusion.

[1] Kempston Disc Interface manual: https://k1.spdns.de/Vintage/Sinclair/82/Peripherals/Disc%20I...

[2] Amstrad Disc Drive Interface manual: https://www.cpcwiki.eu/imgs/3/3f/DDI-1_User_Manual.pdf

[3] Etymonline entry for "disk": https://www.etymonline.com/word/disk