Any good science does what it can with the tools available while acknowledging what it us unable to see. Time, and therefore history, is much stranger and much more complex than the usual linear model, as you mention - but I see no reason to conclude that all history is doubtful in a nihilistic sense - that is to say, I don't think that because we can't know it All, therefore we know nothing. Or because we can't know the full truth, therefore everything is a lie. There is an option between these two extremes - to be where we are, See where we are, and move in the best possible direction, towards truth and the All.
So the use of historical research in 3D is to get as close as possible to the true story of whatever puzzle we're looking at. This story can never include everything, and so it will always be limited. It will be limited by the available sources we have access to, by the frequency fence, by our own biases, overt manipulation of texts, etc. We can put pieces of the puzzle together as best we can, and also acknowledge we will never have the full picture.
There is also the many worlds theory that there might be infinite simultaneously co-existing dimensions, which means infinitely co-existing historical puzzles which occur side-by-side. So if we accept this hypothesis, as the C's seem to indicate we can, things get impossibly complex. Streams of reality converge, then diverge again, leading to all kinds of strange phenomena. There is also 4D bleedthrough as well. So this is another limiting factor, a metaphysical one - our story of the puzzle is generally limited to its exploration this world, and this timeline, this reality, as it appears to us.
As such, Laura's focus has been on THIS timeline. I see no problem with that, as I don't think anyone in 3D would be able to write a cosmically 'correct' history due to our many limitations listed above. To Laura's credit, she has written an excellent history of the truth of Christ. In other places she has also extensively explored the weirdness of alternate timelines, contact with ourselves in the future, time loops, as well as the effects of other densities and dimensions interacting with our own. She is one of the only writers I've encountered who has gone so far into both history of this reality, and also the hyperreality in which ours is embedded. So yeah, I see no contradiction here.
