The temperature rating of insulation is about heat generated by current flow as well as heat imposed upon the conductor by the surrounding ambient just as you said.
Some more examples:
Most luminaires require a specific insul temp.
Flourescents 90deg
Some incandescants with the bulb base up and wiring compartment on top - 90deg and higher
Romex is required to be 90deg conductor type because of the ambient.

Larry LeVoir
City of Irvine, CA