I'm the forum troll that said that and it wasn't a fake, it was a mistake.The Ancares rumour is around every year. Two years a go it was a fake rumour spread by a forum troll. Last year it was allegedly dropped because it didn't fit in the route with the two mountain stages in Asturias. So I won't believe it until I see it in the news.
We already know the finish in Lekunberri after S.Miguel de Aralar. That's the climb where Aru took his first Vuelta stage win in 2014 ahead of the three amigos and Froome, who did a superb (IIRC his first) yo-yo show.
And there's also the rumour that Unipublic has taken positive notes of how well the last two mountain stages this year did work.