What’s particularly frustrating is that the only thing that separates one from the other is the inclusion of a $20 reversing valve[1], and some software that can use it.
Well, that and you tend to split heat pump systems instead of pumping around warm air to pick up efficiency. And the design of the condensers, etc, is a little different for efficiency and to cope with e.g. condensation outside.
The AC unit can do heating if you just run the pump in the opposite direction. It is just a feature the manufacturer did not bother to install/wants extra money for (it is literally a single $20 part for the valve).
Obviously they are not the most efficient heaters as they are not designed for it but they would still work.
[1] https://en.m.wikipedia.org/wiki/Reversing_valve