Yeah, I should be careful to not make it appear as though there were so clear a delineation when Jobs returned. His software engineering team got to work reshaping MacOS (as we know it now) but he seemed to this software engineer to be focused on hardware and "strategies" initially.
Aqua, the new UI, came down from above soon enough. Drawers, toolbars were new UI elements that arrived. In time Jobs' designers were going through the shipping apps with these new UI elements with changes for the engineers to implement.
Certainly by the time the iPhone had arrived the transition to marketing (and design) calling the shots was complete.
Apropos Drawers: The may have looked a little bit silly back then but today almost every Mac app main windows has a big grey sidebar, so that in Exposé view almost all windows look the same. Drawers got an unfair rap, I think.
Aqua, the new UI, came down from above soon enough. Drawers, toolbars were new UI elements that arrived. In time Jobs' designers were going through the shipping apps with these new UI elements with changes for the engineers to implement.
Certainly by the time the iPhone had arrived the transition to marketing (and design) calling the shots was complete.