catch dig trials?

First and foremost I'd like to state I don't care either way if these events were still going on. I of course would definitely like to see my best against the best in any competitive environment, I like competition and would no doubt have loved these events. Although I do have a ?. I was just lookin at the dogo fb page and reading alittle bit mostly just lookin around, but what is the difference in a catch dog trial and letting a dogo find and catch 1 in a 20 acre pen that's supposed to mimic the natural environment. Not looking for an argument just askin a ?.