Also from you,
This seems to be a pretty absolute statement.
Assumptions and presumptions are made all the time, and are necessary to develope the questions needed to drive research. But, they must always be acknowledged as presumptions and assumptions.
If we apply our modern way of thinking and reasoning to someone with the morals, ethics, social standards, and societal situations of the 18th century, and say to ourselves, "this is what I would have done and how I would have done it," and call it historical fact,,,, this is wrong. It is still just a best guess, a hypothesis based on our current situation and the way of thinking that goes with it.
These are all still modern people, not 1st person accounts from people at the time. Their thought and opinions may not be pulled out of thin air like those of some folks around here, they may be based on reasoning from examining some extent artifacts, rifles or accouterments, but, they are still just educated presumptions.