>Honest question: How could they claim damages from someone to whom they've granted permission?
That's actually the underlying rationale here, although it isn't explained well in the linked page. There is the possibility of an implied patent license grant (or waiver) from the licensor in a license that is silent about patent rights, for exactly the reason you state.
But CC0 is different, in that it grants permission to use while simultaneously being explicit that there is no implied patent license (or waiver) granted.
That's actually the underlying rationale here, although it isn't explained well in the linked page. There is the possibility of an implied patent license grant (or waiver) from the licensor in a license that is silent about patent rights, for exactly the reason you state.
But CC0 is different, in that it grants permission to use while simultaneously being explicit that there is no implied patent license (or waiver) granted.