I've found this to be true as well. My daughters test gifted in writing, english, lit but not math, my son is stronger in all subjects, exceptionally strong in math. I've heard that is how it is most of the time. One subject peaks more than others.
There are also different levels. My daughters tested gifted but my son tested exceptionally gifted. I didn't know there were levels at first so it was surprising. My son is as far above his sisters as they are above the norm. They usually come from gifted parents as well but my husband and I are not gifted. So, you never know why or how it all happens. I've noticed my son is strong on whatever area he is into. Your children might pull a 180 on you half way through their schooling. That is always fun. You are convinced it's math until they get into history. Then pow, change of direction.
My son seems to exhaust areas and move on and my daughters seem to have leveled out in their teens to one subject area. So, you never really know.


DUDE:
I know that there are different thought processing modes involved which can play to various strengths and weaknesses, but on this subject of different levels of giftedness, I wonder how much different levels of interest play into it. After all, isn't it the sharp levels of interest in different kinds of learning that drive gifted learners to their achievements in the first place?
I agree, it seems to be true in my house. smile