Sometimes the fear of the dark hole scares some dogs more than the quarry at the end, but I like to get dogs comfortable around holes by letting them watch then letting them have a run about, a dog has to learn when to say no at earths which are empty, and only by checking empty and live earths will it click in its head what it's job is in the hunt. I guess it's just different ways that people do it, but who's right or wrong? My opinion is which ever works best for you and your dogs are working week in week out them that's the correct way for you.