Yes, and CUPS was used on macOS, from which iOS was forked before Apple releases the first iPhone. And from that same year (2007) until 2019, Apple employed the creator and chief maintainer of CUPS, which is presumably how they got their hands on the cups dot org domain. Then (as is typical of Apple's treatment of open-source), Apple stonewalled outside contributions and public releases became increasingly sparse and insignificant. So the creator and longtime ch8ef maintainer of CUPS, now outside Apple, created a new fork under the OpenPrinting banner. Thus CUPS became 'Apple CUPS' and the 'CUPS' everyone else cared about was now OpenPrinting CUPS.
My point was that Apple's language on the website indicates that they probably use CUPS on iOS and iPadOS, not that that language describes CUPS' origins or is informative about the nearly three decade history of of the software or the current landscape of its forks. (Although in fairness to Apple here— a company of which I am not a fan— 'developed by' doesn't mean the same thing as 'authored by' or 'created by'.)
My point was that Apple's language on the website indicates that they probably use CUPS on iOS and iPadOS, not that that language describes CUPS' origins or is informative about the nearly three decade history of of the software or the current landscape of its forks. (Although in fairness to Apple here— a company of which I am not a fan— 'developed by' doesn't mean the same thing as 'authored by' or 'created by'.)