I was going to type out my policy but yours sounds word for word what I'd say lol.

I have a policy in place and MOST families do okay with it. However, potty training isn't black and white and what works for one kid might not for another and IMO, it's a very case by case situation. If a child TRULY didn't understand that a pull up wasn't the same as a diaper than I'd consider a different approach. For sone kids, it can take months while others take a week. If it was an approach that was taking too long or really disrupting my care to the other kids than I may even consider asking the parents to take 1-2 weeks off and train THEIR child.

Luckily, pull ups have never been an issue for the kids I've helped train