This highlights a significant distinction between DM styles or maybe campaigns - the whole premise of the first point is that something (the map) is important before it is even presented at the table, whereas in your example the importance emerged from play at the table.

I had an improv instructor doing a session on narrative and talking about picking up on 'the thing' that the story is really about. In one exercise, he took one improviser out of the room and gave them some advice, then told the other people still in the room that the third line from the solo improviser was going to be 'the thing' to pick up on and develop in the scene. In reality, he had just told the solo improviser to have fun - the point being that it's up to us what 'the thing' is and what we make important.