Gee Dog, I appreciate that!! Of course you know but a lot of folks will do that and won't pull the hammer back far enough for the bolt to clear the cylinder surface and mark it. Pulling the hammer to half cock is the only time it's "safe" for the off hand to turn the cylinder.
The only problem with that is the safety position on c&b revolvers ( as well as converted revolvers)is between chambers. Pulling the hammer to full cock advances the cylinder and of course locks it in battery. To engage the safety, the hammer has to be lowered from half cock while the cyl is held in position with the off hand. I agree with you as far as cartridge revolvers with Colt type actions. There again, with a safety notch, the trigger can be released to allow the hammer to rest in the safety position. Bolt reset should happen before the safety notch is engaged which will allow you to go back to half cock and rectify the situation- either unload or locate the empty chamber.
Mike