Just had our PTC (resistive electric) heater replaced in a 2018 3 with 110k miles. Sure wish it had a heat pump, but we don't suffer much range as we live in a mild climate.

does the newer one use a heat pump?

Oh yes, the entire heating/cooling system is quite a beautiful bit of engineering. a very elegantly designed “supper manifold” and heat exchanges that can push or pull heat from any device to another in the vehicle. They don’t even have heating elements anymore, they just run the motor less efficiently to produce more heat!

Yes, they do. All the newer teslas use heat pumps (as well as most other EVs these days).

A lot of them it’s still optional which says a lot about their small scale.

Yeah, the old one heated the battery through similar tech as heated seats. I think the only problem with the tesla heat pump is that it doesn't function well below 20-30F. I'm not sure if that's all heat pumps.

Well, the problem with the heat pumps in my house, is that near or below freezing temperatures, the outdoor unit has the tendency to freeze over, then either it has to run its resistive heater, or intermittently cut out and blow some cold air inside. It's rather uncomfortable.

I'm not sure you can get away with a design that has to sporadically turn itself off, and melt itself down in an EV.

Something is wrong with your heat pump. Mine works fine during cold snaps. It doesn't blow cold air during the defrost cycle.

Perhaps yours is undersized, or otherwise not designed for cold climates?

Heat pumps on cars can go well below freezing without any issues.