I may not be completely understanding your position, and you may know substantially more about heat pumps. I was looking for hard specification numbers.
I would also suspect that by knowing the refrigerant type, if it has vapor recirculation tech like the Prime, and if it is single stage/dual stage/infinitely variable speed powered, etc. that this will give you some ballpark comparative ideas of efficiency, at least relative rankings.
Definitely an amateur on my end regarding heat pump systems, but can we say that if a fixed/residential heat pump system and plug-in vehicle heat pump system have the same refrigerant, recirculation tech, variable speed features, etc. and we know the HSPF/COP/efficiency curves of that residential unit, that the plug-in vehicle heat pump system therefore has identical efficiency specs?
My guess would be probably not off tremendously, but to get a heat pump system into a vehicle requires miniaturization/component engineering compromises and placement of components in perhaps suboptimal locations thus reducing efficiency, no?
'19 Model 3 SR+ (own), '19 Leaf SV (leased), '12 Plug-in Prius (sold 3/19), '16 Leaf SV (prior lease), 11.43kW Solar PV (16MWh/yr real production), 20.5 SEER/13.0 HSPF ducted air-source heat pump, 3.70 UEF heat pump water heater, Induction Cooktop