Not until the Outlander forces Valkorion to kneel does he recognize that he can dictate the rules in his own mind. Before that, he adheres to the rules of reality, as blatantly shown by the fact Valkorion was surprised the Outlander was willing his way to victory after they fought.
Thus, it makes absolutely no sense the Outlander would will Revan's abilities and sabers into play. That would be inconsistent with the cutscenes and would, as Sas put it, be outright weird. If it were the case, the Outlander should have visualized all possible abilities, an army of allies, and omnipotent powers. The alternative option, in which Revan and Shan actually aided, is not only far more likely, but also a fitting end to their characters, so I don't see why Sas is actively opposing it. Note that the Outlander himself stated Revan may be aiding the Alliance passively in KOTFE.