I think it important to remember that it was Justice Clarence Thomas's Concurring opinion in Trump v USA, in which he chose to write only so that he could include that direction to Cannon within his opinion. Thomas had suggested that the appointment of Smith as special counsel raised a potential violation of the Constitution’s provisions on appointment power, and how an office may be created.
“If there is no law establishing the office that the Special Counsel occupies, then he cannot proceed with this prosecution. A private citizen cannot criminally prosecute anyone, let alone a former President,” Thomas wrote.
As near as I can tell, Special Counsels have been appointed for quite some time now, with no objections from SCOTUS. Surely this can't only be because it's Trump. Surely! Tell me the Supreme Court is not so corrupt as that!