They're likely leveraging a number of guidelines. Primal is multi-platform, and apps that are can let users access content, subscriptions, or features acquired outside the iOS app with the key condition that these items are available for purchase within the iOS app via in-app purchase. Primal frames these as pre-paid zaps, and when you put all that together with a few other guidelines then it's likely they are just taking a savvy approach and it's not Apple misunderstanding what Primal is or does.
Discussion
I stand corrected. Incredibly confusing, though.
yeah it seems like a grey area, but hey if it works
Seems so. The pre-paid zaps framing is savvy because for Sats that are sent in to the in-app wallet from outside, there’s nothing else you can do with those Sats in Primal but zap, in which case they can be defended as externally-purchased pre-paid zaps, or else transfer them out, which is allowed under other guidelines anyway, like how zapping a profile can be seen as a transfer and not a tip. So there's really nothing that those sent-in Sats can do that's not defensible with some effort.