Perhaps it’s just a leftover marketing motif?
"The spelling disk and disc are used interchangeably except where trademarks preclude one usage, e.g., the Compact Disc logo. The choice of a particular form is frequently historical, as in IBM’s usage of the disk form beginning in 1956 with the “IBM 350 disk storage unit”. "
Looks like Raw Story, Rolling Stone, The Daily Beast, The Independent, and whatever that middle one is have reported. Ground is suggesting all but the latter is left-leaning.