Well ["warm up, main reason is the valve train is the last part of engine to receive oil. Less wear on valve train if idles until oil gets there."]
Yep, on DOHC cars like ours, we need the oil all up on those cams and buckets. That is why when anything is just barely out of spec you get tap dancing Leprechauns in your engine, or worse a river dance; until about 90 seconds or so and the oil flows better. I only had a Tap dance once for about 7-10 seconds, but never had it again and I don't plan to stress those components.
We started to hear this "don't let the car warm up" when the gas crisis first came in the 70's and the Jimmy Carter told us to put sweaters on and turn the heat down to 65 degrees in the winter.
I looked at the car care myths and most are fair and balanced and some are not.
Car Care Myths And The Real Story - Car Care - All Cars - Motor Trend Magazine
The real concern is the EPA folks don't want people putting more un-burned fuel in the atmosphere for pollution and stuff.
As to their clear coat myth busting, NOPE a treatment like TST Teflon is better than waxing your car. Once you have Teflon coating you never put wax on. Only cleaner and more Teflon. I had a 9 year old truck with TST and 135k miles look brand new and sell in 4 hours on Craig's list.
My 2008 truck still looks brand new, no wax, only cleaner. And my Mustang has TST as well, no wax.
In that article, they are "Iffy" on the lead needed for pre-72 engine valves and say you "can get by", Green Bias again.