I have been married to a non-talker for over 50 years. I can only remember a few times when he has allowed himself to cry. He does not know how to discuss issues without clamming up or losing his temper. And yet I have stuck with him since I know it "comes with the territory."
My dad was an engineer; they are famous for clamming up. One of my sons is an engineer and behaves the same way until some straw breaks the camel's back. Gut is right; it is the way they are wired.