Real butter or I-can't-believe-it's-not-butter, or margarine, or yellow shortening? Or maybe butterflies are made of all of the above, with each being a different species of butterfly...
No, I meant that that which is in the Duffer encyclopaedia is not unquestionable truth. It represents only the common beliefs of the Duffers. And sometimes those are in error.
We all get things wrong at times! I mean, I thought the refrigerator was a fish once! A big one, but still. And there was the day my sister drank vegetable oil instead of orange juice. She still remembers that mistake distinctly.