I agree with the Professor. However, most people do not literally mean doing many things at the exact same time. Therefore, he's really just fussing over technicalities in the definition.
As far as multitasking as we know it, and its relation to Aspies. I worked at Waffle House for about three years. I have managed to handle a full store alone (2 waitresses didn't show up, another left, manager was horrible). That meant taking all the orders, keeping them in order, cooking them, and serving them, while also making sure glasses were filled at a reasonable rate, etc. It was very difficult and happened during my first 3 months as a cook. I was raised in a kitchen though, so my brain wasn't going as haywire as if I was trying to organize a ton of school work, like I am doing now. I also worked in a teleconference call center for 3 years. That was another story, trying to follow different scripting for 30 different calls that are all coming in at random in the same 10 minute time frame . . . yeah, didn't take them long to find me another position. That didn't do much better so I laid low and held the job as long as I could.
Asperger's Syndrome to the side, there are some things that we will pick up that we can do very well and others that just don't click.