Did I handle this situation correctly?

[SanDiegoSteve]

Unless the coach is interfering, blocking your vision in A, or the other team's coach is complaining of his being outside the box, I would suggest that you ignore such a minor detail. I certainly is not worth your going out of your way to enforce.

If the other team's coach complains, then enforce the rule for both teams and don't let either team's base coaches stand outside the box. But leave them alone unless one of them complains.

You really don't want to go out of your way to look for violations as if you were a police officer. That will get you a very bad rep quickly.