Window unit heat pumps are basically not available (Carrier doesn't appear to offer any either after a brief search). There are a lot of people who would replace an air conditioner with a heat pump who can't afford a full house heat pump. Until you give them reasonably priced window unit heat pumps they are going to continue heating their homes primarily with #2 fuel oil. That will require mass production of smaller heat pumps and competition to bring the price down.

Functionally yes but the VRF (variable rate flow) which leads to more efficiency gains is a bit more added on top just an inverter valve. Otherwise the heat pumps would be cycling on and off. That’s also why ACs are typically oversized here in the US. Because they turn on one massive load for a little while then turn it off (cycling). With VRF they’re running steady at a variable output over longer periods of time.

Yeah, Carrier has been making heat pumps for quite a while now. I'm not entirely sure when they were first introduced, but when I worked there a few years ago the heat pumps were far from a new addition to the product line.

Their capabilities simply have not compared to the models being put out by Japanese companies like Mitsubishi, Fujitsu, and Daikin. Hopefully they can step up their game.