Correct. But the Appointments Clause says “but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments” - which says that to appoint an inferior Officer, you need statutory authorisation.
And this is part of the crux of the dispute - there used to be an Act of Congress authorising the appointment of special counsels, but it expired in 1999 and was not renewed. Supporters of Judge Cannon’s decision - not just Trump’s own lawyers, also conservative legal scholars such as professor Josh Blackman [0] - argue that with the expiry of that statute, there is no longer any Congressional authorisation for appointment of special counsel as “inferior officers”, and hence Jack Smith’s appointment is unconstitutional. Conversely, Smith (and the DOJ and A-G) argue that statutory authority can be found in various other provisions-I know one thing they’ve pointed to is a few “left-over” cross references in the US Code to the now expired independent counsel statute. The crux of the dispute is whether those “left-over” provisions are sufficient to meet the constitutional burden
There's another legal distinction, though; "principal" and "inferior" officers.
https://www.law.cornell.edu/constitution-conan/article-2/sec...
Unfortunately, the Founding Fathers never really explained what the exact difference is.