Well if you rely on running Android apps, you still rely on Android.

Actually, if you rely on the app, you really on the Android SDK which is not open source.

Now if you could run AOSP but your own apps built with an open source SDK, that would be a different story. Some people seem to really want to do that with PWAs. I personnally tend to hate webapps, but I have to admit that they can be open source.