While having respect for both maintainers and pilots, each may approach their operation of the aircraft differently. Generally, if a pilot starts the engines of an aircraft, the pilot's mind has at least the possibility of flying the aircraft in their mind. Thus, by instinct, the pilot may go through a more complete mental process, in checking that the aircraft is actually ready to fly, or at least run. The maintainer is very unlikely to be intending to fly the aircraft when they start it. So their mind, on the maintenance task requiring running the engines, is not thinking to prepare it for flight, so selection of systems for flight may be overlooked, as flight is not intended, even though that system is needed for ground operation (like hydraulics, for brakes and steering). That does not make pilots superior though, they sometimes operate aircraft without thinking enough about maintenance. The pilot might start up, and power away on a loose surface, where a maintainer would be thinking more about FOD - 'cause they'll have to change out the damaged parts!
When I, as a pilot, have taken on a ground run maintenance role, I have arranged to have the aircraft tied off to a ground anchor for ground runs - I don't want to have to worry about brakes holding - unless the maintenance is to check them!
You gotta get your head into the proper mindset before you start.