No and that’s not what I claimed. What I’m saying is that if you tell someone accustomed to Celcius “it’s 42F° outside, oh by the way fahrenheit goes from 0=really cold to 100=really hot”, they have no idea about the actual weather.

obviously, but nobody was saying that, so i'm not sure why it's relevant.

This is like explaining what a door is to someone, only for them to remove the door and go "well now what's it supposed to do?"

“Really cold” and “really hot” are completely subjective. They depend on the climate you’re used to and come down to personal preference even.

not strictly? 0f is cold enough to require wearing additional layers if you don't want to freeze and die after a long enough period of time. 100f, while more livable, is still rather hot. Hot enough that you can't really do hard labor in that weather. Even people who live in climates that are really hot know this, and there's a reason they often wear really specific clothing, or end up having darker skin. Although that's evolutionary advantage at that point.

Unless you took someone living in finland, and someone living in australia. Although deserts aren't really a fair comparison here either. They can get quite cold as well. They're obviously going to have a bit of a different reaction, but i doubt it's going to be significant enough to break the scale. It's probably going to shift one way or the other a little bit, but that's to be expected.

Percentages of subjective temperature tell me nothing. 20F° would basically have to be 20% warmer than “really cold”, right? Intuitively I would have guessed somewhere around 7°C (nice autumn morning), turns out 20F° is still way below the freezing point. The idea of 0F° and 100F° does not, in fact, help me interpret these values “with no prior understanding”.

again, you're applying celsius logic to a fahrenheit problem, and then being surprised when it doesn't work. You don't know what 0f is, not because fahrenheit is stupid and bad, but because you don't use it. So you're trying to estimate into a system you don't know, and then you're complaining about my generalization when it's your translation that doesn't work. It's clearly evident because you even say "20f is way below freezing" which is not at all true here in the fahrenheit lands. 20f is just below freezing here. well below freezing happens when you crack around 10-15f. Way below freezing is quite literally, about 0f.

The idea of 0F° and 100F° does not, in fact, help me interpret these values “with no prior understanding”.

no it doesn't and thats because you have an anti thetical world view that you're trying to apply to it. This breaks the application of the heuristic very evidently.

It’s simply not an intuitive frame of reference - except if you have at one point learned what the numbers mean.

sure, but my point is still that the 0f-100f is a broadly applicable heuristic that should roughly hold true. i believe if you convert these numbers into celsius, which is how you would correctly apply this heuristic, you would see something roughly equivalent to -20c and 40c, which to me seems to line up with how celsius peeps seem to experience temperature.