Yup, that's the gist of it. The prevailing theory was that the inquisitors were retelling what was actually supposed to be a joke but the cultural differences between their ecclesiastical training and folk humor was such that they thought it was supposed to be a literal account.
What kind of joke, from any culture, involves an old lady and a nest of writhing dicks? I cannot even begin to conceive of a humorous angle to that mental picture.....