Has the truck had it's first oil change yet? It may have a thin "break-in" oil to help seat the rings, or the excessive idling may be preventing the rings from seating. The owner's manual or maintenance schedule may address a break-in procedure and oil change schedules. In many shops those manuals get lost or thrown away very quickly.
If the shop isn't concerned about the fuel consumed during all that idling I have to wonder why they are so worrier about a little oil consumption?