I simply chose the furthest canon point even if Ritsuka is not the center. As for the newly revealed powers, Seimei is unique as far as Sacrifices go and is also an unreliable narrator so it's unclear if what he says about being Sacrifie is true or is just specific to him as no other Sacrifice exhibited such abilities so it's sort of unknown right now if what Seimei is saying is true. I am as unaware about the newly revealed powers as other readers at the moment.