DS8 had some abilities which were clearly out of the norm, and he was actually behind with other things, like his speech. He couldn't put two words together, but he could whip together a jigsaw puzzle. He also has some abilities with memory that I consider bizarre. When he was in preschool he could barely hold a pencil, but could draw outlines of states. He could name states in order from north to south from memory (even though he never spent much time looking at maps). Turns out he is 2e and has developmental coordination disorder, causing delays with certain skills. This can occur in "typical" children as well. They are just a bit slow in terms of brain maturation. This is one reason IQ is so unstable if measured before school age.
It's also possible that your DS is gifted in math but not so much in other areas.
