FireOS is heavily modified AOSP (Android Open Source Project) so there is similarities, but vast differences as well, especially around how TV apps works and how notifications do.
FireOS does not support the Leanback library, which is a principle component of Android TV.
It’s actually the same APK for Android Mobile, Android Tablet, Android TV and Fire OS, with different sections enabled when you’re on specific devices.
Fire OS devices will not activate any ‘Android TV’ components of the app.
