First the Butts case has a very limited circle of suspects and none of them seem to have ever had any connection to the Ramseys.

Second, hairs of various types are often found at crime scenes. Indeed it is the most commonly found item at a crime scene.

With nothing unique about the placement of the hair at the JonBenet murder, I would not term it a 'signature item'. We don't even know if the pubic hair is related to the crime. And with a paintbrush handle having been used, it seems unlikely he even attempted to perform any acts that would be likely to have left pubic hairs at the scene.