The flutter.dev page got rewritten to be more "marketing friendly" a few years back. docs.flutter.dev is still maintained by the engineers however.
Regarding who exactly contributes to Flutter, it's all on GitHub, so you can see the actual committers, e.g. https://github.com/flutter/flutter/graphs/contributors https://github.com/flutter/engine/graphs/contributors https://github.com/dart-lang/sdk/graphs/contributors
As for flutterfoundation.dev, it appears to be just Matt? Who used to be employed at Google and reported to me on the Flutter team but is no longer.