But to serve Michael, Rocco would have been removed from Clemenza's supervision. That would have to be explained to Clemenza somehow. I just don't see how Clemenza who was in on the Corleone family from day one could have been kept in the dark.
If Rocco's official position was to be Michael's bodyguard, he didn't have to be under Clemenza's control anymore, which was an easy explanation. Just as Neri, Rocco probably reported to Michael directly.
