Dragon Age had an unreliable history by design.
People had an imperfect view of the events that have shaped their world.
However, from the very beginning of Dragon Age, there was a secret document refered to as The Black Codex. It held the true history of Thedas. This helped to steer the half-truths, misunderstandings, and lies that shaped the world.
The story of the Veilguard was going to reveal so much actual truth, it meant the Black Codex could no longer be a secret.
This series of illustrations was a way to explore the major events of Thedas' history, so that we could easily refer to them when designing murals, costumes, architecture, etc...
Beat boards like this were meant to be "single frame storyboards" to quickly communicate a big idea.