These guys have multiple separate indications of forgery just on the document alone. If one turns out to be explainable, it does not in any way mean that the report of forgery is false, or that the whole investigation is invalid. Sorry you can’t see that.
You don’t get it. It’s not that it’s “explainable,” it’s that it indicates the claimed meticulous investigation was careless or deliberately misrepresenting the evidence.
When that happens, it taints the whole investigation by the Cold Case Posse. It taints all their findings. And it make them look foolish, and everyone who bought into it breathlessly without checking look foolish also.