Yet my place, that was built in the last decade, only has AC. If I want to switch to a bi directional heat pump, they’ll need to access the lines to add insulation, which would have added maybe a couple hundred dollars to the building cost but at this point would involve opening up walls. All that on top of the several thousand to buy the heat pump unit itself plus a conversion or new air exchanger.

The technical difference between an AC and heat pump is so trivial that IMO ACs that aren’t heat pumps should be banned.