Crafter is basically a fail path if you don't meet the requirements for any of the other hero types.Prologue class is determine by good score, bad score, and sex score. I'm not the dev, but I'm pretty sure this isn't a bug. There is a specific event where this is decided by your scores.
Also as a question for the dev, I'm personally curious about the craftsman path. Is it just an easter egg or are their any plans for it?
I needed something there, otherwise the game would just end on an error for people that somehow made choices that didn't align to any of the other class conditions. There were never any plans to expand on this class, because he basically has his canon ending before the main game begins.