I'm not familiar with the Player's Secrets. As I remember, though, in the recently-hashed-out hierarchy of canon materials, PS's fall pretty low. If we are going to abide by any standard of canon and use the canon hierarchy, we should be explicit about when we wish to depart from canon material with major new fan-based contradictions/revisions, or when we are trying to explain the canon further.

I understood most of our discussions to be trying to further expand upon the original existing material in a somewhat rigorous, academic fashion. That approach precludes radical departure from the original game setting without being explicit about the fan-based nature of the departure.

As for the Erebannien, High Mage Aelies and ilk haven't been around as long as the forest. It was protected by Imperial decree under one of the last Roeles, if I remember correctly.