2nd reproduction step should say to "Put the 'articletoc' bbcode at the top". I think I accidentally put the actual bbcode when writing this out, so it kind of screwed up the list

Hey there :) Prose articles are not part of the article "content" system which is the reason that the Article ToC doesn't work for them - this is not a bug - it is a lack of a feature though - one I completely understand.   A good course of action for this would be to add a feature request so we can see the community desire for this and take it from there!   In order to do that head to: https://www.worldanvil.com/community/voting/