Russell,
You could be right, however, little story. Back in the 90's. I was the weekend guy at Northrock Lanes, in Wichita well before Billy Murphy took it over. I was learning how to drill and was practicing on old balls, my stuff etc. But I'm sure I screwed up a few balls "as I learned". Anyway. One Sat, one of the regional pba guys brings in a ball looking for Tom (the owner) to drill it as he did all his stuff. I told him he was out of town at a tournament. He wanted some unique drill. I told him I was new at this, and had been trained at what he wanted but never actually drilled it. He could come back or take his chances. He wisely came back later.
People have to learn to drill. And people screw it up. I have had guys that drill my stuff on a regular basis miss my stuff by 1/4 inch or drill it right handed (I'm a lefty).
When you are a one man shop, you can get distracted. So you hire some help.
And in this age of dual angle and other modern drill patterns, if you have some new guy learning to drill, they screw up. It is possible. Not every pro shop has sent their guys to proper training.