@manton Here's the bit that's tripping me up:
To qualify for the entitlement, your app must:
... Offer in-app purchases when distributed through the iOS or iPadOS App Store in the United States storefront ...
"in-app purchases" can only mean Apple's IAP.
It's like with Sign-in With Apple, in which if you offer any other sign-in service you are forced to offer Apple's alternative. They're treating your single link with the same level of distrust and hysterical caution as the providers of the "Sign In With..." buttons.
As for auditing your books; yes, that sounds right. I remember Vincent got hit by App Review because they didn't like something on his website. Perfectly healthy and normal ecosystem. 👍