So, Ashe is the ~chosen one~ in the end, the scene here makes sense as Fran tells the ancient story of Raithwall and how he left those words for her. 

But we know Vaan was a candidate. Those words were meant to whoever the Occuria wanted, and being Raithwall’s heir(ess) has nothing to do with the trial that awaits them. The door would have open for Vaan too. 

True, the current stones react to Ashe’s presence, her blood or her anger. But all of this is merely the will of the Occuria. For them, being a royalty or the lowest of commoners matters not. What matter is how useful you are for their own benefit.

[512/?]