I haven't talked to a child educational psychologist lately (I imagine that would be quite renewing to spend some time in a kindergarten even if only virtually, don't you?), but I don't think biological claims about elite abstraction is the only way when it comes to explaining more and more with less and less for mathematical education. For example, non-symbolic distinction and indication operations are far more fundamental than symbolic manipulation, and using that is a bottoms-up foundation more in keeping with constructivist understanding exhibited by math exemplars.

Cognitive disparity is because of compounding investment of attention and metacognition in development, preferably in a self-referential non-symbolic universal way because intuition is partly based on sensual metaphors and embodied cognition. Everyone has issues distinguishing ungrounded concepts if they don't have a map of them from their attention previously..

Mental rigidity (aka "fragile perfects") is a fairly common phenomenon for math anxiety, whereas Grothendieck advised uninhibited playfulness to deal with uncertainty. The perceived difficulty of mathematics is a social phenomenon rather than organic comprehension limits on abstraction ceiling.

It is the social aspect of math that is the superintelligent part of it, which transcends the genetic determinist perspective. Civilization advances because education transforms the breakthroughs of genius (which all children have ultimate capability for) into the baseline intuition of the rising children by sharpening their attention. Math is supposed to be a democratization of human understanding, that's why the Greeks were so keen on deduction and why proofs are for systematic communication. If a stupid-ass computer can do math, so can any human being.