The "reader app" exemption Apple introduced in 2022 is merely about an entitlement to link to your website for account management, isn't it ([1])? But your argument sounds as if each Spotify purchase made through the app is or was taxed 30% by Apple, which would seem anti-competitive. Could someone clarify what Spotify or its users have to pay to Apple?
Spotify has not supported IAP for premium in a decade and therefore has never paid Apple any fees besides the $99/yr developer fee.