Not necessarily. I'm not sure what McC's permanent grade is, but he only held General for a bit more than a year.
Officers usually have to hold a rank for a certain amount of time to retire at that rank. I had to keep LTC on for three years to keep it in retirement.
To retire at four-star grade, an officer must accumulate at least three years of satisfactory active duty service in that grade, as certified by the Secretary of Defense and confirmed by the Senate.[31] The service secretaries and the Secretary of Defense may reduce this requirement to two years, but only if the officer is not being investigated for misconduct.[32] The President may also reduce these requirements even further if he so chooses.[32] Officers who do not meet the service-in-grade requirement revert to the next highest grade in which they served satisfactorily for at least six months. It is extraordinarily rare for a four-star officer not to be nominated to retire in grade, or for such a nomination not to be confirmed by the Senate unanimously.
I retired as a lowly O3-E, so the general officer shell game didn't affect me. ;-)