TIL You don't lose more heat from your head than anywhere else on your body. The myth came from a 50's army field manual with some suspect experimental procedures.

Yeah and I don't think OP's labelling this as a "myth" is really clarifying anything. It's not "true" or "false": it's an overly vague and broad generalization from one study. It's like if someone told you "You eat half of your fat at breakfast". Is that true or false? Well, it depends a lot on which "you" you're talking about and which day you're talking about, but in any case it doesn't make much sense to generalize it into some sort of bizarre universal truth or falsehood.

This is what I always thought the "more heat from your head" thing was about!

The article also mentions another experiment done about 20 years ago with swimmers and the same body heat measurements, with results showing that heat loss was correlated with area exposed. It's a poppish article but the background behind the myth was the big TIL for me

That's absolutely incredible! What a wonder science is!