>How can the historian’s claim be an insight into today’s culture, views, and lives if the claim is well reasoned and substantiated by the known facts?
Because the facts are evaluated through the lens of the historian. The lines of reasoning, logical conclusions, and modes/methods of investigation are all, inherently influenced by how the historian was raised, trained, and how/when/where they live. It's just part of being human. It is impossible to present literally anything without it being biased in some fashion. In deciding what to report and what not to, how much weight to give to historical accounts versus other historical accounts, what sources to chase down, even where to look in the physical world, we are imposing our own beliefs on the event.
That's what I'm trying to get across.
Not about this specific article, or the concepts of gender fluidity, etc. But the actual process of investigating and reporting historical facts. It is an inherently biased process. It just is.
And I believe that was the OP's point.