The old Benz diesels had what was misnamed a hand throttle. These engines had fully mechanical injection systems and were unthrottled, so all the driver controlled was mixture. It was often necessary to use the loud pedal to richen the mixture and get a start in very cold conditions. Why truckers like to idle their engines is beyond me since once a diesel has been run and warmed up, it's very easy to restart.
With any engine, increasing engine speed greatly reduces warm-up time.
If I follow BMW's direction and run my old 318i up to operating temperature once a month during winter storage, it would take about forever at idle.
At 2000 revs sitting outside the garage, it takes only a matter of minutes.