I've heard of it before, though "the internet" says its a speed advantage, I always heard it as a workaround to laws limiting round count in a magazine.

Quote:
How many rounds are legal in NY?
seven rounds
New York limits any person to putting seven rounds of ammunition into a magazine, unless the person is at an incorporated firing range or competition recognized by the National Rifle Association or International Handgun Metallic Silhouette Association, in which case the limit is ten rounds.Apr 2, 2021



You can't carry an 8 round revolver or a magazine fed pistol that can hold 8 or more rounds in the magazine. So you carry two 6 round revolvers and the second one is your "new york reload"