With hounds, the biggest challenge in training them is teaching them what not to chase. The instinct to trail, bay up or tree is bred into them, to focus only on the target species is not. So yes, particularly with younger dogs, you're going to have some "trash" races. I'll guaranteed the hound owner was not happy to find his dogs bayed up on an elk.
The latest GPS tracking collars most houndsmen use today also has a built in electric shocker so if a dog does stray off the intended species you can fry their ass. Nothing like 50,000 volt surge to make a hound say I'm sorry. If the hounds you observed were so equipped I'm sure they got the treatment.
Typically it only takes 2 or 3 electric sessions to break a dog off a particular specie, but there are still the coyotes, skunks, porcupines, and on down the list to deal with.