I conflated nothing. Overactive thyroid is one cause of fast metabolism.
The rest of your rant gets us to the point of talking about "wrong" (using your word) versus "elevated". A diagnosis of hyperthyroidism generally, would require markers above a certain level. Hypothyroidism generally would require markers below a certain level. That leaves a range considered "normal". A range. That means that someone can have a more active thyroid than another person, and both be within "normal" range.
Nor is the thyroid the only thing that affects BMR. There's evidence (and I'm not doing your searching for you - since you are inclined to take pot shots at the method of the search, do your own damned search) that BMR can is genetically influenced. There are other factors that are easily controllable (diet, exercise, sedentary state, etc.), but there are at least two (thyroid and genetics) that are not under the control of the individual.
But, once again, you knew most of this, and were simply arguing to be arguing.