I think what is more confounding is that such signs can be both mild ASD and brain immaturity/slow development. In particular, I am thinking about the child of a family friend who appeared to me clearly mild (beyond borderline) ASD and was classified with an IEP for ASD by the school district in K. Interestingly, this child also had a couple of savant traits (give him any date and he can give you the day of the week immdediately, etc.) that disappeared after the ASD signs improved substantially many years down the road. It struck me as odd that the savant ability disappeared as his behavior improved substantially into the "borderline" range - one of those mysteries of the brain.