So I'm not familiar with why that particular judge was criticized, but you'll note that the entirety of arguments and discussion surround the brief and response letters which were submitted to the supreme court. It's possible that Cannon was stepping outside what was presented, which would warrant criticism. The supreme court never steps outside what is presented, except when it's necessary to understand what is being presented - for example they may call upon other legal text or rulings in order to fully frame what is and is not in scope with regards to the presented case or to understand precisely what a particular lawyer is arguing for or against.

But I also think that the fact that the supreme court is the final court which gets to have say on a matter lends them to pontificate in depth about some issues that other courts may not be given latitude to do the same because it may address issues which are currently working their way through the court system or may be called upon as a matter of jurisprudence in the future. The entire text of every decision they make can have consequences on lower courts and understanding the limits and the spirit of law they weigh in on and as of such it's important to fully understand the exact claims being made and appropriately scope where the response lies and whether certain issues could or should be weighed in upon during that case.