No.
There are three kinds of authorial insights for a work in progress.
Statements of intent: These are subject to change
Statements of fact/explanation/clarification: These are revelatory, canon statements about why who did what and why. These are things the reader waits for the author to reveal, because they are already part of the story. What happened at Justin's that last day, for instance. These should be treated generally as canon factual.
Statements of "I never considered that, and will now make something up."
Butcher has no intent of bringing in the Oblivion War, so appearances by Oblivion War opportunences are flavor text for the reader- the reader knows the "why" of the Archive, if theycread the shorts. For story purposes, in the "main" plot, it has been sufficient to know the "what" of the Archive.
Shorts are canon, but it's poor writing practice to make them prime narrative required. They're expansions, not story progressions.
Now, if Butcher WoJ that Peabody's swamp-smelling portal was to where Cowl was whrn accessing the Deeps, that's a WoJ of the first type.