I booked a 4-segment trip, all DL flt numbers but NW metal. Called NW and gave them my NW worldperks number, got assigned elite seats. At the time I was silver about to make gold and the agent advised me to call and have it re-entered. Her comment was "it will help get the upgrade earlier". The trip got cancelled at the last minute but I'm assuming the upgrade would have happened based on what the agent told me.