Well, I’d say it’s mostly Android-compatible. It depends on how picky you describe Android. Is it just an OS? Or is it a platform and ecosystem actively promoting the inclusion of proprietary libraries that communicate with Gobble services integrated with the OS? If you look at the Android website or any version changelog, you’ll see the later. If you look at developer docs, you’ll see the later. If you look at the app ecosystem… well, you know the answer already, 
Furthermore, Android is a registered trademark that cannot be used for products or whatever that doesn’t include Gobble services and pass the GTS. The issue here is we don’t have a name to refer to the other kind of systems. We could say they are AOSP or AOSP-based, but Android is AOSP-based too. 
TL;DR: FP Open/Sibon is strictly not Android, and it’s fine it has its own name.