I expect whoever coated the remains with that red cinnabar stuff died rather early, probably with tooth and hair loss and severe mental issues. Perhaps this fate was expected but given that "mad hatters" were a thing until fairly recently, people can be a bit strange when it comes to dealing with poisons.
The guide notes point out that only the most sacred rituals involved this red mercurial stuff. I'm not surprised. It might be rare but rarer still will be people willing to deploy it unless that fate is considered a good way to go.
That tour is a remarkable use of the technology.