Many new cars have electric heaters for the air venting into the cabin. In that case their statement about confusing warm air with a warm engine would be true.
Especially small diesels which take too long to warm up for passenger comfort.
Yes, but the whole argument about washsing the oil off cylinder walls is irrelevant to diesels, as excess diesel lubricates, rather than dries cylinder walls.
Could be. I've never encountered one, and I think they would be a dead loser where I live. In fact, the thing I dislike most about our electric vehicle is that it's heaters are so wimpy. Probably wouldn't matter if I lived South of the Mason-Dixon line, but at -20F, they are awful.