Cattle are kind of a different cup of tea. Everything we do with dogs has some risk, but cattle are pretty darn dangerous. When our club brought in cattle for a trial two years ago, one of the dogs competing broke her leg, and that’s not terribly uncommon.
You can look at the list of GSDs who’ve finished ASCA’s WTCH (Working Trial Champion) if you’re interested. To finish, dogs have to title Started, then Open, then Advanced on all 3 types of stock, including cattle. So any WTCH GSD will have had at least 6 successful cattle runs in trial, with at least two of those completed at the Advanced level. I absolutely agree that trials aren’t the be-all end-all, but working unknown (to the dog) stock at different locations does demonstrate ability and work ethic. The stock absolutely get jazzed up on trial day, as well, so that adds another layer of complexity.
Cattle lines of BCs (and of course ACDs) come out of the womb with certain traits that aren’t common in GSDs, but there are definitely dogs who have done it.