I believe the traditional explanation behind the wise men is that they inherited prophetic traditions from Prophet Daniel when he was in Persia, i.e. no prophetic powers were attributed to the followers of Zoroastrianism per se. In fact, Tradition seems generally silent about the existence of any prophecy or revelation outside of the Old Testament patriarchs and prophets. Non-Israelite religions seem to be treated more as true to the extent that they reflect the kind of truth about God that can be understood simply from observing the world, but it is not the source of any supernatural revelation. So I'm not aware that Plato or Aristotle were ever considered saints. Exactly what happened to them when Christ preached in Hades only He knows. I know there's this one church with "icons" (without halos) of Plato and other philosophers, but that really doesn't seem representative to me.
I still feel the Prayers by the Lake to be kind of dubious. I note that it was endorsed by St Justin Popovic, but again this was in 1922. St Justin's anti-ecumenist polemics seem to date from much later, and this still appears to fall into St Nikolai's early, ecumenist period. I imagine St Justin was always under the influence of St Nikolai, and parroted whatever his master believed. This work seems to be the product of a certain Orientalist "traditionalist" mania that you see in e.g. Frithjof Schuon. They like to reject Western religion as too "rational", while anything Eastern, whether Christian, Muslim, Buddhist or Taoist, is considered to reflect the same "perennial religion", because it's "mystical".