You mean https://nosmero.com/? In a brief look I couldn't understand how they're doing paywalled content, I also don't know who is behind that site, but I wish they considered https://github.com/nostr-protocol/nips/pull/2156 and provided their feedback. It's independent of payment methods and not tied to zaps or anything.
A generic standard that multiple clients implement would be better than some specific platform that does their own custom paywall scheme.