Let’s be real, Lucas also directed ROTJ.
Are you on crack?
It’s commonly believed Lucas backseat directed much of the film, due to Richard Marquand’s shortcomings handling such a large cpmplex FX laden production. IIRC, Lucas directing some second unit sequences is documented. He was definitely on the set much more than he was on Empire.
He executively produced a number of films which I assume he had a lot of input into but he is not credited as the director for them either
The Wizard of Oz had five directors, but only one got screen credit. Gone With The Wind had three. And then there’s Poltergeist…
There must be a valid reason why only one person ever receives the acreditation, perhaps they input more than the others? One would assume.