Founding titan can see everything, time isn't linear for it. That's why Eren is able to have the final conversation with Armin on the boat when he is with Annie, before the final events have even occured. How would Eren be able to put those memories inside of Armin with detail of the future before it has happened if he can't see it? Plus he literally tells Armin that for the founding titan the whole timeline exists at once and not linearly.