The source being me, in Chicago and the notes I've taken over the years from talking to people in the business.
A lot of people in New York and Chicago think the local water is a major component to the dough. That being said, I probably should have been a little less serious about it in my post. I am not 100% convinced either, but I do like to hear the arguments for/against this theory and people in Los Angeles (for example) have said their water sucks and is not helpful in making better pizzas. But it could also mean they just don't know how to make dough!
A Malnati's staff member confirmed my guess at what I thought buttercrust was at Malnati's.
I also got some insight from a former manager at Pizzeria Due, just to throw out another source to deep dish making.
Stuffed Pizza is my least favorite pizza. That useless, gummy layer of bland dough on top just under the sauce is nothing special and I just don't really care for the stuffed recipes I've had overall (though I had an amazing one at a Nancy's once, but I can't remember which one and I never had anything close since).
Here's a funny story. I had heard that a place called Art Of Pizza was named Best Deep Dish in the city by the Tribune or Time Out Chicago or something like that, so I had to try it. I went there with my brother around 10pm on a Friday night to check it out. When we got there, we were told they were closing soon and only could sell us slices. When I looked at the slices, they had Stuffed, and a really doughy pizza with a glob of rubber cheese on it (ok, THIS is the most hated kind of pizza to me). I asked if they had their award winning deep dish available. They said the stuffed was it. I was mad. I pointed out that it was stuffed, not authentic deep dish, but they called it deep dish. So I ordered a slice anyway, figuring it must be good. My brother and I ate our slices outside and we were actually mad while we ate what we thought might have been the best stuffed slices we ever had! "This is not deep dish! Those idiots got it wrong. Boy this is great stuffed pizza, but I wanted deep dish!"