nOffers (lnurl-pay equivalent) are payable by any npub, the keys in the offer are just that of the receivers node service, it's designed to be ad-hoc nDebits (lnurl-w) started as npub-bound, a budget was allocated to the remote key by the wallet for claim. The new `k1` field makes it now so that the claiming npub doesn't need to be known in advance, so for someone to claim a prize they would just need the static ndebit pointer (relay uri and key of the service) and the one-time use claim code `k1` So in this case the k1 could roll to match the desired cooldown