I’m pretty sure that is also the case in the US. These incidents are either caused by some sort of defeat device (I have seen weights that wrap around the steering wheel, no idea if they work), or people who have just gotten good at resting a hand on the wheel and not paying attention I think

We don’t tend to use air/air heat pump systems in the UK, even for new builds, always air/water.

Because of lower water temperature output of heat pumps compared to the gas boilers they replace, usually you need to increase the size of radiators to be able to achieve a room temperature change in a reasonable time. What is being referred to as efficiently, is actually just a measure of performance of the radiator, not actual energy efficiency.