That being said, where else would this kind of content have worked where the everyreader wouldn't have given up after the third or fourth paragraph of dense medieval historic record?
A Medium post or something would be more natural for this length of text, but it also deters people with the possibility of a ten-page story. 60 tweets might be absurdly long, but at least you know it's not going be 200. So the format is dumb, but I think you're right - it offers a guarantee to readers who don't want denser pieces.
I can look at the scroll bar on an article and decide if I want to continue after a couple paragraphs, I can't tell from a tweet that starts "5/" if it'll go to 8 or 60.