edit : I am not a Googler, but that's what I gathered from talking with them

Here is what is happening :

A couple of years ago, when the dart team failed at getting their runtime embedded into the browsers, they started searching for a problem to solve. They thought they had hit jackpot with multiplatform development. So they started working on Flutter. This is all entirely independent from the Android team at Google.

The Android Team at Google continuously improves their own framework, hence the jetpack set of libraries. One of the new libraries they have been working on and that is now public in pre-alpha stage is JetPack Compose. They have hired one of the engineers behind React and had them work inside of the Android Team on a "React like UI framework for Android".

The official direction of the platform is what the Android Team is doing.

Flutter is interesting, with all the advantages and caveats shared with other multiplatform tools like ReactNative.