Nothing precludes actual fierceness rather than strictly fitting to an archetype. I used to illegally street race for cash. I can detail strip most Glocks, ARs, and AKs, and fire each without occluded aiming. Grandfathers were both competition military wheel gun marksmen. There are such people as nerdy bodybuilders.
I took the SAT-I without any preparation (absolutely zero) and aced the math section, 5 on AP Calc BC with minimal preparation at school; no coaches, no practice tests, and no bootcamp classes after school. My school was supposed to be good but it sucked in one particular way as it picked me through testing to represent a math tournament but sent me completely unprepared in the fields and subject matter, it was embarrassing. I was usually the lone white dude amongst mostly Asian and Indian overachievers who had rich af parents with every sort of coach and social help. I road a steel-framed bicycle to school 4 miles each way everyday, they had hand-me-down BMWs and Mercedes parked in the school parking lot.
The other issue is like BUD/S and specops, the people told they couldn't or were unsuited also tend to be the ones with the most heart. Someone can't wish to be more fluidly-intelligent, but they can become more relentlessly-resourceful and dog-with-a-bone. Wisdom, experience, and mastery trends to swamp raw intelligence as someone ages... plus, fluid intelligence tends to decline.