I've learned not to worry about it
The one thing I will do is not use pull ups or diapes for kids who are only using them for BM's. If I have kids holding BM all day until their nap time pull up, and the pull up is dry with the exception of the BM, no more pull ups and close monitering until they have gotten the hang of it. Some kids are very fearful of pooping on the potty so I try to be very positive and reassuring.
Good Luck!