Not a mechanic, but I always teach my piston students to do these checks on the two axis units because you can get into trouble with bad pitch commmands. Roll-only units I do not bother with the preflight. Some of the older S-Tecs are quite unreliable, so if it has pitch control consider a preflight mandatory. And if stuff falls off the airplane from doing the check, then obviously you should taxi back and squawk it.