Congress can not appoint special prosecutors.
Congress can authorize themselves to appoint a special prosecutor. They’ve done it before.
You are playing with semantics. Congress can appoint an independent counsel which is a synonym for a special prosecutor.
The appointment is a process by which the DC Circuit is COMPELLED to select a prosecutor that is acceptable to Congress.
So the best that can be said for your end is that it is a bit of an indirect process. But again if there is a strong leadership group in Congress, they will keep tabs of who the DC Circuit is offering for selection.