You couldn't be more wrong.
Android is open source and can be used by anyone without giving anything to Google.
The only restriction is Google's apps and the trademarked Android logo.
Amazon cannot use them without paying a license fee to Google.
The name "Android" simply refers to the OS.
But that doesn't change the fact that it IS an Android device.
The underlying frameworks are still pure Android. Their Android App Store would not work on the Fire if they were not using proper Android frameworks.
Customizing the front end doesn't change what it is... another Android device.
So despite Amazon and Google insisting the Kindle Fire is not an Android device, you obviously know more than them.