Does anybody know the thought behind the ul label on light fixtures requiring supply connections to be rated for at least 90 degrees? I know that it does not pertain to the wiring in the box mounted in the ceiling due to a code seminar I attended many many years ago but I do not remember the exact meaning for it. Does it apply to the wires connected to the sockets or what?
Thanks
Ron

The specification does, in fact, apply to the wires within the connection box.
When UL tests a fixture, temperature measurements are an important part of the testing. Where there might be a problem, UL will require that wires in the area be of a certain insulation, the fixture be marked "Not for use inside residences," etc.

Ordinary THHN qualifies as 90 degree wire, so there's not a problem. What do you do if the requirement is for, say, 105 degree wire? Well, you end up having another j-box a couple feet away, and running the expensive hi-temp wire those last few feet.