The thing is,
the actual leaks from developers who have dev kits have told us the NX device has a Nintendo-grown OS. If it is derived from Android, it's going to be as recognisable as Android as VitaOS and OrbisOS are as recognisable as FreeBSD.
There's also no chance Nintendo will include the Google Play Store and Google Play Services on their device. In doing so they completely cede control over to Google, which they'd be doing by adopting Android in the first place. Nintendo would have to make sure that their specific, special version of Android gets updated every year to match a new version of Android, and they'd be conflicting with Google's own decisions in where it leads its Android platform.
Google’s iron grip on Android: Controlling open source by any means necessary
Then there's the notion of including the Google Play Store on the NX in the first place: Developers will have zero incentive to actually support the NX hardware when bringing over games that have an Android version, having two stores will confuse customers and expose customers to software that's poorly optimised for the NX hardware or simply isn't designed for it, and Nintendo will earn nothing from game purchases, if a customer picks the Google Play Store instead of the eShop for Android.
That's entirely the wrong approach in my eyes. From Iwata's comments 2-3 years ago, Nintendo is instead focusing on making its software more portable and its development environments more modern so it's easy for devs to bring over their work and make it feel at home on the NX.