More like, "There is one Microsoft App Store, but apps on Amazon's Android App Store will also appear in Microsoft's App Store so you won't as a developer have

More like, "There is one Microsoft App Store, but apps on Amazon's Android App Store will also appear in Microsoft's App Store so you won't as a developer have to publish your Android app two places for them to show up in two places." I would bet, for better or for worse, these Amazon Android apps will share metadata as well, so you'll see the same "Star" rating in both the Microsoft App Store and the Amazon Android App Store, but that's speculation on my part.