This is driven by the EU forcing them to allow alternative payment methods in the Play Store.

They are trying to avoid it, but I doubt the EU will let this stand:

https://www.developer-tech.com/news/google-alters-play-store...

Android is open source partly because they can fund it from Play Store profits. Google is thinking that their Play Store profits are going to be cut, and they want to make the profit up elsewhere - and importantly, maintain control of the platform. This is their method.

They've already used this playbook in the past with Google Play Services, and even before that when they abandoned all the built-in open source apps (Email, Calendar, etc.).