Maybe Lucas didn't keep Kurtz abreast of everything that he was thinking about. Lucas is known for his quiet, reserved demanor. For most people all they ever got out of him was "faster" or "more intense".
Lucas says he ran out of time and money and chose to live with the way his shots turned out rather than try and do more shots. Kurtz says he doesn't understand why Lucas would say they couldn't have done more, but then again, Lucas said his biggest problem with Kurtz was that he never said no to anything. As I understand it, the reason they stopped working together was because of the fact they went so far over budget with Kurtz as producer.
I don't think anyone disputes the solid wall of time and money they were up against while making ANH. At the very end they had to split into 3 film units to wrap everything up because the Studio was about to pull the plug if they didn't finish ASAP.