I agree with that. I was mainly getting at the point that the "shape of the damage curve of a conductor" was not likely to be the driving reason for the 25% adder because a higher temp wire insulation could reduce that concern. I concur that the heat dissipation and temperature limitations of the breakers themselves are probably the main reason for the added 25%.
OK, so maybe "damage curve of a conductor" isn't the correct term.
What I means is a curve that indicates, for a given current, how long it is OK for a conductor to experience that current before the OCPD activates. That curve clearly has a different shape than the trip curve of a thermal-magnetic breaker, in the usual thermal environment of a panelboard. Because if you select a trip curve that protects the conductor well for time scales on the order of minutes, you may get nuisance trips with time scales on the order of hours.
I don't see how increasing the insulation temperature helps with this, I would think the shape of the conductor allowable current-time curve would be similar across different insulation temperatures.
Cheers, Wayne