thank you for your service

How upset do you get when your buddy disables auto and proceeds to slam back and forth between full heat and full ac while claiming their shitty dial dj set is somehow waaaaay better than the computer?

I assume you mean EVs with heat pumps? I don't know of any ICE vehicles that do this, seems inefficient to waste mechanical or electrical energy when you have perfectly good waste heat to use upon reaching operating temperature (though you may need to use an aux heater before reaching that, particularly on diesels)

My car is a diesel so it takes a long time to warm up in the winter. They added an electric auxiliary heater to compensate. The air is really hot within seconds.

My car is an EV, so it definitely does this because there’s no excessive engine heat to use.

Fun fact (well, I suspect you know this already, but some didn't, I had discussion with someone arguing with me that this is not true):

AC and a heat pump are basically the same thing, AC is just pumping the heat outside instead of inside.

Also when you say modern cars I am assuming you might be talking about EVs. Using a heat pump requires less energy than using resistive heating so it could be energy saving measure.

ICE cars on the other hand can get the heat from engine "for free" (not really, but since the heat will be produced anyway whether you use it or not, so why not use it?) so a heat pump might make a bit less sense in them.