They're a part of the same suite of apps that provide the "Android experience" (Google experience, whatever -- the thing that most consumers think of when they consider Android). They manifestly have a profound connection with each other.

And let's be clear here lest there be any confusion -- zero customers want a vendor to do anything different, and the only reason some vendors wanted to is because they could double dip: Pitch the Android experience and get the market inroads, while getting some Bing or whatever payola to "force" that on a consumer.

The same is true of the other claim-

Then they said "You can't use Google Play if you try to help develop any android forks."

Google's argument, whether honest or not, is that if you need a consistent representation of the Android experience that you're selling to consumers. If the GS8 has the full Android experience, but then the GS8P has the Android Fun Store and Bing Search, this can seriously dilute the market opinion of Android and cause consumer confusion.

This is absolutely not at all clear cut. It is incredibly nuanced. And if we just go around clubbing everything coarsely, why does my BMW have a BMW entertainment system? Why couldn't I choose Alpine at the dealer? An entertainment system is not an engine, right? I don't want to go down the road of absurd analogies, but if you're seriously presenting the notion that this is clear cut, you are not really thinking about it much.

As an aside, Google has had the same policies regard their suite of apps since day 1 of Android. Since the very beginning. When iOS absolutely dwarfed it. When Blackberry reigned supreme. When I was hefting around my sad little HTC Dream and listening to the John Gruber's tell us how doomed it was.