My son sounds exactly like yours, we've just done the diagnostic for autism at Lurie, although we started therapy through EI a few months ago (he already qualified because his speech is so delayed).
The appt was just one hour long, and based on that one hour where he didn't want to partake in any of the activities they asked him to do (combination of shyness and not being interested in things that aren't very logical to him ie feeding a teddy bear with a miniature baby bottle), they decided he should receive an autism spectrum diagnosis, which they later switched to PDD in their written report.
Literally nobody who works with my son agrees with their finding in any way, and EI weren't actually able to act on any of the recommendations that came with it anyway (they recommended he get 30 hours of ABA therapy a week, he gets 1.5 hours a week of speech and OT). In fact, at Lurie they told me that EI in IL doesn't even really have any of these therapists, you'll probably have to go through your insurance and possibly drive to WI for one.
My son also started preschool this fall (early start program at our park district) and if anything, this has been the biggest help for him. In the last month he's started saying words I never even thought he knew, it's like a switch finally came on for him.
I've learnt a lot about asynchronous development through my older child, who we finally discovered is HG a year ago. All of my son's therapists agree that he is most likely so busy learning letters and numbers that the other stuff fell to the side, but as his brain grows he is finding space for the other stuff. I also think that it's a big logic thing with him, when he doesn't see the point in something he's just not interested.
At the end of the day, EI isn't interested in what your child can do that is past their age, they're concerned with what goals they aren't meeting. They didn't care that my son could name all the letters on the blocks they gave him to stack, it was that he wouldn't push them around like a choo-choo train like they wanted him to.
I wish you the best of luck with the appt, and hopefully you'll have a more constructive outcome than we did!
