Guys relationship with mother

I know they say that you should watch how a man treats his mother to see how he will treat his wife. Well I'm gonna be honest here..(thanks anonymous option)...my bfs mom is not the nicest lady. She can have a real inconsiderate diva attitude sometimes. And he is her only boy, so she is a lot harder on him than his sisters. And because of this he is often quick witted and sarcastic with her. Also when they get to nagging at each other, they sometimes don't talk for a month after besides an occasional text. It's not anything horrible, just saying overall they do not have the best relationship. And the wives tale of how that reflects his behavior as a husband gets me wondering. What is the community's opinion on this?? What is your Hubby/fiance/bf relationship with his mom?