Android will be most likely only the base for the NX OS. I doubt it will be fully compatibel with android devices.
Nintendo use android because they don't want to create a new OS for NX from ground up. To build a full new OS would be very complicated and time wasting , because consoles OS are much more complex these days than two gens before.
So Nintendo use a free OS like android as the base and creates their own libraries (graphic system, input system) on top of this.