The only problem with engineers (including myself) carrying out ground runs, is that a lot of the time they are running the helicopter "after" maintenance, repairs, component replacement or an overhaul.
This could lead to an out of balance incident if anything was installed out of balance etc , new blade, main rotor head, straps, etc.
I have been on a ground run that was "walking" around the helipad quite briskly with tail rotor balance equipment being dragged along the ground behind it. The main rotor blades had not been aligned correctly after strap replacement.
It would have made no difference if a pilot was running it.