No, well-taught martial arts don't. Injury can.
The following suggestion is made sight unseen, and does not constitute medical advice or diagnosis. I say it because you describe a postural change I have observed many times in the past, with a common cause; other/different causes are certainly possible.
The posture you describe corresponds to a postural compensation for an injured rib on your right side, towards the back (I'm guessing 8 or 9, sight unseen). Such injury probably occurred some time ago, ask your wife when she started to notice it. Other past injuries may also be involved; when, instead of resting and recuperating, we continue to train (or otherwise work hard) after an injury, we adjust our posture to favor the injured area(s), and learn to function that way. Unless we make a conscious effort to correct such compensatory postural changes after the injury has healed, we may continue with the distorted posture.
Unfortunate that contemporary fighters are not taught to read posture, one can tell a lot about an opponent's weaknesses from a brief evaluation of stance and movement. "Know yourself, know your opponent"; one should also be reading one's own posture (and all other indicators) in order to monitor one's own health and capabilities. Such self-reading also gives us insights on the conditions of others.