It doesn't really matter, regardless of whether or not we agree with the rules, jeans are clearly prohibited in the tournament:
4.10.1.3. No players with t-shirts, jeans, shorts,
sneakers, baseball caps or inappropriate dress are allowed
in the playing area. Any requests to wear national or
traditional dress shall be approved by FIDE Supervisor.
Having bad rules written down doesn't make them immune to criticism. It's a silly unnecessary rule that shouldn't exist, and while Carlsen doesn't deserve any special treatment, being consistent in enforcing a bad rule isn't better than not having the rule in the first place.
