The crazy thing is I even left it open ended with a question mark, inviting people to enlighten me. And what I got is precisely what I wanted, along with a ton of downvotes like I was an ideologue or something. I'm an ideologue about some things, heat pumps not being one of them. Regardless, now I know that there are, in fact, heat pumps that are designed to work much better in cold climates than the one I have, and that there are plenty of cold-climate folks who find the performance of the heat pump to be sub-par in extra cold weather, requiring supplementary heat.