I think Jasnah covering her safehand in the Cognitive realm has more to do with propriety than anything spiritual. She is, after all, a princess, and she would have been expected to be proper from a very young age.things like always wearing a covering her safehand were likely just second nature to her. I suspect that the reason for safehands are less spiritual and more mundane. It was another way to try and keep women away from Shardblades. We know there were female KR who fought; now women don't fight. Yhe male arts are the ones that involve weapons. Only being able to use one hand would put anyone at a disadvantage during a fight.
Does anyone remember if the women in Dalinar's visions have their safehands covered? That could help us figure out when it started, if not why.