With an SAA you open the gate, not the cylinder. Secondly, what good is looking at a dummy round loaded in a gun going to tell you? Many look just like live rounds.
And far as testing for dummy rounds by dry-firing, that is standard procedure for many movie armorers.
The point is, anyone who actually knows enough to assume the position as an "armorer" would know how to keep the set safe, even from imbeciles.