I get the fact that engineers are great - I have relied heavily on their skills, graft and understanding for many years - but, when it comes to rotors running a non-tied down helicopter by someone who hasn't been taught to fly it just in case, then regardless of what the rules say (written by other engineers I suspect) I think it is plain stupid.
I'm with you. In this modern world of risk mitigation, engineers conducting ground runs adds unnecessary risk. In most companies I've worked for, newly converted pilots will not do single pilot engaged ground runs, so why would an engineer with virtually no "aircraft" training (in comparison) be allowed to do so.