It's not that I'm conflating them (I completely agree, there is surely some(!) unknown(!) base maximum capability per individual), but I am more so challenging this intuition/"epistemically unsound cultural axiom" that "openness" (or logic, or basically any cognitive ability) "is" essentially/largely immutable.

Most people I encounter find (heuristically) this belief/philosophy to be "wrong"/bizarre if not downright offensive, but I sincerely believe that this type of thinking (a bias towards conclusiveness and away from epistemic soundness and curiosity, and this is but one example among many) is one of the biggest root cause problems of problems on this planet. A prime example of where this is causing serious (life and death) problems is with vaccine hesitancy - people love to hate on anti-vaxxers, asserting that they "are" "stupid", but rarely have I encountered a "smart" critic who has the cognitive ability (openness) to even consider the possibility that their perception of the situation is incorrect (if not downright harmful from a causality perspective).

A (likely offensive, as a demonstration of my point) way to think about my stance/conceptualization that might help communicate my frustration: I feel as frustrated with pro-vaxxers (or, ~neurotypical ~Western human beings in general) as pro-vaxxers feel with anti-vaxxers...and ironically (or not), it seems at least as difficult to reason with them (which I believe well demonstrates the ubiquitous nature of the phenomenon).