But the navigation system doesn't appear to have lane planning at all. For example, when I drive with the nav, it doesn't tell me in well in advance which one is the exact optimal lane. Instead, I have to be closer to the junction before it shows a standard lane hint for that turn or junction (the one that shows the lane layout for the junction specifically), which as you point out in your own example, can offer lanes that are "incorrect" if you don't want to have to make last minute lane changes at the next turn or junction.
Thus FSD needs to have it's own macro lane planning function if you want to avoid situations like that. Without that, it's going to drive like a driver relying on lane hints at every turn/junction and not making a wholistic lane plan for the entire trip.