With your foraging example, it does make me think ADHD is a small group/individual optimisation. Prioritising high vigilance and individual productivity over social cohesion.
I speak with no authority. I don’t even know how such a theory could be tested.
What do you think nutritional stunting means?
It would make sense to me that evolutionary there would be different mental development paths depending on the requirements of their situation.
This is coming from my understanding that ADHD is more prevalent in stressful upbringings.
That would normally be called "learning". Also a pretty conventional idea.
With learning, though, you'd want to explain why something becomes immune to further learning at a certain point.
Or maybe it’s learnt like you say, I think both areas would be worthy of researching.