I get what you're saying, but do people in the UK really believe that you do "know the details first-hand"?
Fair question. You'd have to say Brits know far more, at least, than Americans, to be able to put this whole thing into some kind of more balanced context.
You don't have to be sure of every word or to believe what you're told.
Many aspects of the RF are part of the fabric of the country and regularly part of the calendar - you see it and live it. You experience it all more directly. Similarly Americans know much more about American presidents, and politics (as an example) to make more balanced assessments than foreigners could. (Balanced is the best we usually get, as opposed to pure objective truth.)
Personally, I don't think I know either side well enough to be
sure of that pure truth (and I've said that throughout). My doubts are based on the way that this whole interview has been presented and on several of their previous, very public, actions in the past. There are holes in their arguments that don't rely on believing 'the other side's' word. I'm just here to chat about those doubts.
It's important to know what you don't know, sure


, but that works from all sides.
Or, do you know what the Monarchy wants you to know?
...Ditto for Meghan and Harry!
Like I said, this isn't about just believing one side's word over another. What helps is having experience of their public actions (all persons involved) over time and some knowledge of the workings of the Monarchy (like title bestowal).
Americans know more about America; Brits know more about the UK. ...Not everything, but enough to see a bigger picture.