Uh, I know that. I have been shooting single-shot revolvers for almost 60 years. I have a Ruger .22 single-six from the first year of production and also a Blackhawk .357 from the first year of production in addition to several others. I grew up in the days that you NEVER put six cartridges into a six shooter, always leaving an empty chamber under the hammer ... for safety.
Never heard them referred to as “ single shot”, only “single action”. As to the empty chamber rule, it’s a good habit fer sure, even with modern revolvers with rebounding safety hammers. Doesn’t pay to push yer luck.