Umm... Yeah...
Most of the Pope Joan stuff hit a peak in the lead up to the Reformation - what with all the fun stories of corruption, scandal and such... how else would someone top them - invent a female Pope! Ah those wacky Germans and their various herasies
My personal favourite Pope Joan story is the one about how she died: giving birth to the Anti-Christ
As you can see slagging the Church has a very long and colourful history