Would ground "popcorn meal" differ from regular corn meal? Purely a theoretical question I'm afraid - I haven't experimented (yet). If you take popped popcorn and grind it to a flour, would the result be similar to cornmeal? One difference, I imagine, is that it is in principle ready to eat, as opposed to regular cornmeal which still needs to be cooked to denature the proteins.

Are there things you could achieve with this "popcorn meal" that don't work with regular cornmeal? For example, what would you get if you used this for making polenta? Could you make a "raw polenta" that doesn't require much cooking?
Interesting question. so I pulled out a hot air popper (you wouldn't want to use a oil popper to try this.) and put some popped dry corn into a food process and let-her-rip. I wouldn't call the results "masa" but it might be usable for an ingredient in a breading.

I call your attention to the book "POPCORN". It has a nice collection of recipes which include popcorn, and in no case does the author suggest reducing popcorn to corn meal, so I suspect the answer is, "Yes, ground popcorn meal would differ from ground corn."