As I know, many gifted kids have sth that they are "obsessive" with, what is your kids obessive with and how intense is it?

My DS3 is obsessive with numbesr and shapes, he write numbers all day long and everything he talks is related to number, for example,

1. When we have a walk, he always point to the trees and ask me how many leaves of each tree.

2. When he play with lego house, he put all the lego figures asides, and the numbers are bathing, cooking, sleeping, eating, driving, swinging, sliding, etc. One day when I was cooking, I heard what he said, " 9 is sleeping, 7 is driving, he is going to supermarket to buy avocado for 20 to eat, 100 is cooking #51 rices for 30 to eat..." so after a while, i went out and said to him, "30 and 51 already finished their dinner and it is time for xxx (lego figures) to have dinner!" (i am trying to ask him to play with the figures rather than number) but here is his answer "mom, 51 is the rice..." +_+!!!

3. He write his number all days long, design dot-to-dot by himself and ask me to play with (he draws them randomly), sometimes when he was overwhelm, it seems that he write numbers to calm down himself.
Draw digital clock with Date and Temperature.

4. Other than numbers, he likes to play color code and lego, especially loves reading lego manual, as there are lots of numbers and x1, x2.

Actually why I ask this questions is that he went through some developmental evaluations, psychologist said that they cannot diagnosed him of autism as he is good in social interactions with adults, but they cannot rude it out either, as he is not speaking english yet, so they don know how he use of language, and they also worry that his interactions are all related to numbers. In additions, he does fall to the "restricted behavior" criteria of autism.

After going to preschool for 2 weeks, his teacher tell me that they try hard to shift his activities to sth else not maths, but fail.

So I am wondering how intense is the obsessive interested of other kids, will your LO refuse to learn other stuff other than their interest?

My son does like to learn reading at home, but doesn't interest to learn it in school.

Thanks.