The issue is really the amount of heat that the luminaire ports back into the box. Like many things, the owner of a house with old wire is probably going to have to spend more money for a luminaire that handles the heat better and does not require the 90c wire.
I also agree if the HO buys one and puts it up himself, we will never know. I would like to trust that a licensed electrician would respect his craft (or fear a lawyer) enough not to do it.
