It doesn't matter, they are the same thing, just different companies call them different things, and I call them SLEEVE hitchs.
Wheel Horse has both an old sleeve hitch, and the newer clevis hitch. If you was to buy a Wheel Horse sleeve hitch, you'd be greatly disappointed if what really needed was a clevis hitch. Yes, they can be interchangable terms, and different makes applied to the same term to different styles, but that doesn't make the parts interchangable. IMO, it's best to use the correct term for the make you're referring to, it might save some confusion. All that said, there are terms commonly used in the Wheel Horse circle that, while technically correct, are not what the items are called. Try looking them up on a parts list, and you'll never find what you're looking for.