> His primary school principal described him as ‘a happy little fellow who has a clear understanding of the fact that he is different’.

I believe it comes down to intrinsic interest, that he would not consider this something boring he needs to work through, but rather something fun and intriguing to spend his time on.

Disregarding the unusual age in this case, I believe that most people could be significantly better at mathematics than they are, if only they found it interesting enough.