I really don't think it is unnecessary. I re-read it and continuously read the ongoing season 2. This season contains the most information about the twin dragons and why they care for Ian so much. Personally, this is season is longer than expected because it is needed.
I call it unnecessary because I believe it's nothing Ian couldn't have uncovered himself, like, the audience being shown everything directly takes value from the actual main character of the story working to uncover the truth of his situation, like it's a rare case of tell, don't show, for me personally, like, what's the point of the reader knowing all of this if Ian isn't learning it along too.
Brian is already dead anyway, if we survived the Under the Green light and Dear Benjamin Hiatus hells, we can survive Eternal covenant long ass unnecessary flashback season