When the high idle comes down from 1400 rpm, that's the car telling you it's ready to drive. No reason to idle for 20 seconds when you stop. That's just wasting fuel, however small.
No need to wait until 50°C to start driving. You're just wasting fuel idling that long and will take longer to reach that temp than it would just driving it. There's a fleet in Alaska (using HPL) that regularly cranks up in -30°C to -45°C temps. They start it, log the hours, put it in gear, and away they go. No difference in wear rates vs letting it idle to warm up.
Not disagreeing with you at all, but my way makes me feel better. It doesn't actually take long to see 50 C water temperatures, because they are plugged in hours before a winter start, and the water temp is already fairly warm.
They all have oil pan heaters as well, so the oil is warm.
It was -12 C here at 05:00 this morning when several of my drivers came to work, to head out in trucks. I turned on the cab heater, both block heaters, and the oil pan heater, in all trucks that I knew were heading out this morning, at about 22:00 hours yesterday. It was -8 C last night when I was out plugging everything in, and those trucks had sat for 2 to 3 days.