If I was evaluating a jumper, I would want to see them free jump and see their natural form and their enthusiasm for jumping. You would look at a potential cow horse the same as a herding dog, they are either show a natural inclination to want to herd things or they are not.

My friend raises some nice cutting horses and they were showing off some of their foals when we visited once, they would throw the dog's ball into the corral and as soon as the poor dog got under the fence those foals were working him just like a seasoned cutter would work a cow. It was hilarious, poor dog did not like that particular duty but the call of fetch is strong, lol! Some cow horses might be initially timid in close interactions with cattle but will learn to work them, I dunno if that is more of a training issue. Some horses are so bold that they will go after a cow aggressively and even bite off its tail, that is not a good trait for a cow horse. But any breed of horse can be a decent cow horse (likewise some bred for it might not make the cut).

I had one draft cross that would herd chickens in her pen, she would take a group into one corner and go get some more and move them around, I've seen ponies that would herd geese and I have a little mare who thinks it is her job to work other horses down the fence. My geriatric mule perks up when she can herd other horses puts on speed we did not know she had and some pretty slick lateral moves for a 16hh 20+ critter. I haven't worked cattle in a sorting situation with her but when introduced to the neighbor's cattle she stepped right up and was ready to go move them around, even though a couple of big cows faces up and moved at us. Cows also have to be trained to be worked by horses, they aren't born knowing how to interact with horses or vehicles or people trying to move them around. Likewise cutting & roping cattle can get soured or dulled down where they will not work well in the arena, some people use young buffalo for cutting because it takes a lot more to sour them.