I think it is important to remember that there are many different "learning styles" (or intelligences if you are into Gardner's work). Although I teach flat changing with the bicycle right side up, I can see that it might help some folks to turn it over.

Some of it for me is "how I learned" as well as for me it is easier to see where the wheel goes into the drop outs when the bike is upright.

I also think it is important to teach using as many learning modes as possible -- I demonstrate, narrate, guide my students to change their own tire, and I have a handout. Some folks find it easy, others find it challenging, but they all learn with instruction and encouragement (the encouragement part of the show is as important as the instruction!).

Anyway, just another perspective.