We should talk more about these guys. These are the guys who serve as the Literary agents of the Arthurian Romance Narrative, specifically for the Lancelot prose cycle.
Supposedly, they're the reason the stories of Lancelot, Galehaut, etc. manage to reach thw modern day. They're also how the french writers could deviate from previous material, insisting on premise they accurately recorded the happenings and deeds of the heroes not mentioned by Robert, Chretien or Geoffrey.
If you are to write an arthurian story but with your own spin and changes, you can attribute the difference to "they were totally wrong/super-biased/skewed the facts" and say "this is what really happened"
Or, more ambitiously, make up own own "source material and authorities"