Is a valid point. There have been cases where I have been the PF in a multi turbo prop, where the procedure is to apply the parking brake for engines running operations. I don't like the fact that the procedure is written that way, but, I don't have to like everything. So, I'll follow the procedure, but I still guard the toe brakes, and monitor outside for possible movement, as though I do not trust the parking brakes.Especially, procrdures that are contrary to the AFM.
I remember doing ground runs on a G1000 Caravan. It had synthetic vision, so as I sat still on the runway, while the avionics tech did whatever he was doing, I, of course intended that the plane not move. I was spooked, when out the of corner of my eye, the runway strips on the synthetic vision were creeping, it seemed that the plane was creeping. Out of instinct, I applied more pressure on the pedals.
The plane was not creeping at all, it was the slight GPS variations moving the synthetic vision strips around a foot or so, but it was enough to tingle my spidy senses that the plane was creeping.