I like this. It could be thought that his honor could have attracted a (honor) spren. The stone shaman's noticed this and recruited him to become "truthless" as part of the belief system. Something like, for the rest of us to be good (or something) you must bear our sins. Then they helped him make the shard blade.
Sorry if I don't make sense. I've just stumbled upon this site and I'm just getting off work.