I have this child. Solar system, presidents, and all.
When DS was younger (age 3), he was diagnosed with ASD because of the sensory issues and this rage to master focus. However, as he aged, (had multiple therapies to help with challenge issues), his diagnosis was questioned repeatedly. He is no longer considered ASD. The "hyperfocus" which can be found in both gifted and ASD communities has a very fine hair which can be split. The difference (in our experience) is what is done with the information. For example, is it strictly memorized or is the information malleable? Is it strictly facts rattled off or can the information be used to imply or deduce non-obvious features?
At what age was your child's asd diagnosis removed, and what age is he now? I am far from an expert in early child learning, but my son appears to be pretty flexible with the information that he has learned. The pieces build upon each other and he can answer questions that force him to manipulate the data out of the original form in which he learned it.
We also found the reason for the hyperfocus was important. Is the memorization used to help create a world, internal or otherwise, in which all things are predictable and controllable? Is the hyperfocus used to explore and learn, then deepen the knowledge by associating it with other facts that are learned?
I think initially it is just to learn because it is interesting, but then he will "draw" numbers and figures as a calming/relaxation technique. His teacher has sent home pages and pages of presidential date ranges.
It could be that your DC has a very high working memory. When/if you have him tested, you will need to find someone with a good background in both 2e and gifted. Not an either/or as they can't split the fine hairs.
Note: very high working memory brings a whole different aspect to highly gifted that you will need to research should that be the road you travel.
Could you list a few examples of unique aspects/challenges?
