I think they need to have more than 12 rounds if it ends in a tie. I understand the economics and the difficulty in the uncertainty of the length of the match. Back in the day, WCC matches were 24 games or longer.
to have the WCC decided by blitz chess after such a tough slower control format is a shame.
In my mind, Magnus did not demonstrate superiority over Fabby.
"Fixation on rules is childish". No. If we were having a discussion along the lines of "Who is the best Classical Chess player in the World?" then there's an argument to be made for 'both Fabi and Magnus'. However, World Chess Champion is an official Title; an official position. It is governed by rules. Presidential elections are the same way. You can say that one person is better for the job, or one person is more qualified, or should have won, but President is decided by the number of votes a candidate gets in the Electoral college. It's all about rules. The World Chess Champion may not be the best player in the World (see Topalov, Veselin). But you are the World Chess Champion is you won the World Chess Championship according to its rules. And you may make any argument you like for someone being better, or how it should be, but it doesn't matter. Like it or not, that's how the match is decided. @PardonMyBlunders comment is a prime example of what I'm talking about.