You are right to be confused about that claim, but it because the units of the claim have been mixed up. The actual claim is 2 kWh/mile. That is a measure of energy per distance, kind of like gallons per mile.

If a truck is using 2 kWh/mile while traveling down highway at 70 miles per hour, its power draw will be 140 kW -- that is the one to compare to your 2 kW idling or 24 kW hard pull.

My EV uses 0.2 to 0.3 kWh/mile, so 2 kWh/mile for a truck seems plausible to me.