I think he is on the right track but this does vary by product to a degree.
I have always told the painters with my product every + or - 10 degrees
you can figure a change of flash or any other statement in the tech sheet by adding to subtracting 15%.
I think a 10/10 or a 15/15 rule is a fair Gage to go buy because like you say most people if painting at 90 degrees are doing everything written in the tech sheet for 70-75 degrees. Anyway it is in the ball park.
A few years ago we did a sampling on the clears (I have 6) with a temp range of 40 to 110. (35% humidity) Humidity also is a very big factor.
This is on my product and did not test anyone Else's and all products are made different and the core resin is probably the biggest factor as to the reaction. (note of the six clears there are three different core resins used)
The rise of 10 degrees from 65 degrees varied from 11-17% in change up to
105 degrees than changed real fast with much larger jumps.
The reason for the large percentage gap in my product was the fast activators and the spot type clears were showing higher percentages but they are made to cure faster.
At the 100 degree mark everything got off kilter as the core resins I use are low bake resins so that changes everything.
A low bake resin you would bake at say 110-125 degrees for 10-20 minutes where most you would bake at 130-150 30-60 minutes. (just for comparison)
Going from 70 degrees to 40 was very constant until we hit 50 degrees and than there was a big gap with the Turbo, Euro and the universal still staying in range and the other three "giving it up so to speak"
Either way 10/10, 15/15, 15/10, 10/15 are all going to be a fair guide for the home user to use and should be close for most clears and primers and they can't go wrong using any of the Percentages as a guide so they can make general adjustments.
Re: Mud and epoxy all I can say on that one is it would have little or no effect on mine.
This is something everyone needs to know and I don't think it was ever brought up before. Great question.