In driving training, we are taught how to properly yield when there is a yield sign at an intersection, the same rules would apply so there should be no ambiguity. If a car drives through a "normal" yield sign and causes an accident, then the law would put the blame on the person who didn't "follow the rules of yielding" properly. If a cyclist was given an option to treat a stop sign as a yield sign but just blew through it and caused an accident, the cyclist would be held accountable. I'm sure that Idaho has considered this, I was just "adding" to it by suggesting that a modified yield sign be put at stop-sign intersections where the powers-that-be have decided that this intersection is safe enough to allow cyclists to consider the yield option when it is safe to do so.