That question has a couple of answers. The only position less than 1/4 cock is the hammer fully down. It is not recommended to carry a SAA and clones with traditional hammer, and hammer mounted firing pin, with the hammer down over a live round.
Normally, a high primer in a revolver, double and/or single action, will cause the cylinder to bind. If it didn't bind, the primer would be seated the rest of the way by the hammer when it falls, absorbing a lot of the impact. Normally a high primer that doesn't bind would take two hammer strikes to set it off. One to fully seat it, and the second time it's hit will fire. Now this is from a full hammer drop.
The hammer dropping from the 1/4 cock notch, or safety notch, would be highly unlikely to set off a high primer. Very unlikely.
Now if the gun was dropped from some distance, landed on the hammer in the safety notch, it could shear the notch and cause the gun to fire, as lore has it. Hence the load 1, skip 1, load 4 and let the hammer down on an empty chamber.
If it is true that the firearms were regularly unsecured and people were "playing" with the firearms on the set of a western film, there exists a possibility of it being damaged to include previously shearing the safety notch. Once damaged, would the firearm still be operable in the manner in which he described the event?