He is talking about Apprentices, p.40f, Teaching Hermetic Virtues - and playing fast and loose with it. The author of Apprentices wrote here on the forum: Apprentices: In my hands... - #66 by Matt_Ryan - so keep that well in mind.
Anyway, if you are planning a campaign in the 14th century (and, as I assume, before the plague of 1348), Europe has become very different from the Mythic Europe setting in early 13th century. Population has grown, methods of agriculture improved and many, many wildernesses in Western and Middle Europe have been claimed for the plough, for herds or even for noble sports. Society there has also changed a lot: the economy is money-based almost everywhere, towns and cities are more independent and powerful, the Catholic Church is more centralized and better organized.
You have to decide, what has happened to the Order in the roughly 100 years since the classical Ars setting. Wilderness-based covenants in Western and Middle Europe might mostly have vanished. The Gentle Gift might have become dominant in the Order, even just because the remaining covenants - having now a choice between far more candidates for apprenticeship - follow the example of Schola Pythagoranis (Heirs to Merlin p.126ff), Oculus Septentrionalis (GotF p.70ff) or Cunfin (TLatL p.106ff) and do not take in apprentices without it. And the large libraries once hidden in the wilderness might be lost now with their covenants in some cataclysms. You could go as far as having magi answer: "Durenmar? I know no Durenmar!".
So, if a magus with Gentle Gift in a remote British covenant has devoted his life to his inclination for teaching in person, has come up with a Hermetic Teacher Breakthrough and developed it to a level, that reading a tractatus is sufficient to obtain its benefits, he might find more interest than he expected himself, in a greatly reduced Order.
Cheers