Thats the common old rule and one I followed when carrying a single action revolver.Load one, skip one, load 4 more is what we use for our revolvers in the cowboy shoots. This centers the empty chamber directly below the hammer so those using a Colt or Uberti do not have to worry about hitting the hammer and setting one off in the holster. I carry a Ruger Vaquero so it’s not an issue for me to load 6 but the COF calls for 5 shots.
John Wayne even relayed that in The Shootist.