You are off point of the portion of conversation you are quoting. No problem, I will clarify.
The statement that was made is that it is unrealistic for EVs to be held to the same standard for reduction in range while towing, (at this time at least). In other words, and I use this loosely:
The Cybertruck roughly had a decrease in range of 75%, more or less, while a ICE truck, towing the same load would see a decrease in range of 25-30%.
EPA does not have a mpg or range for vehicles over 8600 GVWR, you are correct, but they do for under that range, and ICE trucks would see the same decrease as a percentage, again roughly. I never brought up EPA, I was talking real world numbers from my own experiences towing +10000 lbs with a gas truck.
Does that make sense, or do you need a more specific clarification?