Confiding with our children
It is often the case that a child will have a different sort of relationship with each of their parents. One they might go to if they need help with a practical problem, and one they might search out if they needed to talk. This doesn’t mean they’re closer to either one, just that people have different skills.
So I don’t really think getting upset that your son won’t talk to you about one problem is a particularly mature attitude. If his wife had promised not to share the issue with anyone, and it wasn’t a really big deal then there was no need to tell her husband. He needs to grow up.