I find Revan to be a special case since he literally lived two lives. He had knowledge of the darkside and had mastered it in one life but because of his alignment as a jedi he could not use its abilities to their fullest. Luke had great knowledge of the darkside and probably could have performed many powers if he was a sith. I think defeating Malek and being at least able to put up a good fight against the emperor of the sith puts him at master level for the light.
I can see your logic to him mastering the light, but the 'all mighty creator' himself says it is impossible to master both sides of the force, no matter how special the case it cannot