Nikkei reported in the past that a 3DS XL was imminent, Nintendo denied this, Miyamoto even said the current 3DS (the O.G.) one was "perfect" as is, then three weeks later they announced ... the 3DS XL. lol.
Nikkei also first reported Nintendo would make smartphone games in January of 2014, Nintendo denied this immediately, but like 10 months later they announced they're making smartphone games.
So I do think Nikkei definitely has sources inside Nintendo. However that doesn't mean they are right in every detail, but it seems like they do get the broad strokes correct.
That said, even if this turns out to be true, Nintendo will simply say "we're not using Android ... we're using a customized version of an OS you might say is Android called Nintendroid" or some such, lol.