What we have seen of the Grimoire of the Shadowlands is mostly in-universe perspective.
It means it’s the thoughts of an existing character. It isn’t word of god, in other words, it doesn’t necessarily indicate that those are true facts.
If another character later on poses statements that contradict these, it isn’t a retcon. It isn’t inconsistency. It is merely another character’s thoughts being shown.
Even if the same character later on shows different thoughts, all theories and hypothesis evolve and change. It still won’t be a retcon, for none of that is being shown as factual information.
For instance:
“Everything we had learned from our travels indicated that Oribos was a place of boundless knowledge, where ages could be spent learning from the spirits who venture through its rings.”
- indicated that, meaning it’s the writer’s impression.
“Ardenweald’s function supports our theories that the First Ones crafted the underlying framework for the cosmic forces of our universe: one that would facilitate an endless cycle of Death and Life, which they made central in their creation.”
- our theories, meaning that everything in that paragraph is what the Brokers think, not necessarily what it is.
“The role that they designed for the Winter Queen within this cycle was a vital one, requiring a bond between the conflicting forces so intimate that it is logical to assume that the existence of a reciprocal being who serves as her counterpart can be found as well.”
- it is logical to assume, once more, their thoughts.
There are many, many, many stances where the book clarifies clearly that what is written is what an existing character assumes, ipso facto those aren’t facts, those are fallible thoughts, theories and conjectures and thus the book serves as a window for us to peer into the minds of the Brokers regarding the Shadowlands and cosmology as a whole.
All of that can be contradicted by other characters’ thoughts.
All of that can still be shown to be not factual.
I’ve seen many parts of the community debating as if those remarks were undeniably factual, as if they were “Word of God”. They aren’t Word of God, far from that. And debating with other people as if everything in Grimoire of the Shadowlands was factual would only lead to frustrating discussions, with “inconsistency” and “retcon” being thrown left and right.