Only thing I can figure is, if all you know is wheel guns, you wouldn't be safe carrying semi-auto?? I guess considering semi-auto are in general more complicated than revolvers, so if you have control over the semi-auto then a revolver wouldn't be a problem for you. But that isn't true for transitioning from a revolver to a semi.
That's my thinking on it at least. Too lazy to look up accurate info on it.
You'd be surprised at how many little old ladies, and even some men, bring loaded revolvers with the hammer cocked into our local range and even some local gun shops and once at the police station (I'm sure that this happens all over the Country). They'd been messing around and didn't know how to decock the weapon. I've seen this with a few shotguns too.
When I see someone suggest that women are better off with a revolver, I reflect on the times that I've seen that. Not as many semi-autos come in with problems like that. Could be that it's easier to figure out how to get all of the bullets out by either dropping the mag and emptying the chamber, or maybe they just keep cycling the slide until the gun is dry. It could also be that more inexperienced people just stay away from autos.
If we tell inexperienced shooter to buy revolvers, maybe we tell them to get DAO.