Spotify also does audiobooks now!
…and because of the in-app purchase requirements from Apple and Google, buying one involves getting linked out to a website. Given the limitations at hand, the experience is about as seamless and well-polished as one could hope (this is Spotify, after all).
But it's still non-standard. Which means now we get end-user walkthrough guides like this one explaining how to do it.
The whole IAP situation is just becoming absurd. Apple and Google are clearly set on continuing to fight any changes on principle, one scorched-earth inch at a time. Eventually, somebody is going to get frustrated enough to steamroll these policies with either regulation or legislation. But that's basically how we got into cookie consent banner hell with GDPR, and I don't think anyone is going to be thrilled with the outcome this time either.