"While Mullenweg says there technically was a roundabout way for an iOS [user] to find out that WordPress has paid tiers (they could find it buried in support pages, or by navigating to WordPress’s site from a preview of their own webpage), he says that Apple rejected his offer to block iOS users from seeing the offending pages."
That's harsh to say the least. Wordpress only wants to give purchase options on their website, outside of the apps. Apple is forcing them to adapt their app. Unlike Epic Games' case, where Apple is probably right, here they have got it wrong.