When I actually read the ROP comments it does look like they are saying embedding wire in foam degrades the ability to shed heat far more than just being in a cable jacket, a pipe or simply bundled together. This actually seemed to go back to an SE issue that came up where a bunch of them went through one hole and burned up. Granted 310.15(B)(6) might allow an SE to be overloaded to start with. (like 100a in a 4 ga).
I would like to have heard some of the arguments on your "can" fight.
"IC" does stand for insulation contact.
I suspect the first indication of a problem would be blinking lights as the thermal cycled. What that would be doing to the foam is another issue. I agree with you. Being slap up against fiberglass is not much of a problem but plastic foam can go right up.
I guess when we are all LEDs we won't care about luminaire heat that much ... as long as it is not an Edison base.
