Interesting thing to consider is that reverse cycle airconditioners are notoriously inefficient compared to dedicated cooling or heating units..
Reverse cycle units can use anything from 2 times to 5 times the power of a dedicated unit on cooling
Do you have a source or a concrete example for that?
The most plausible explanation I can think of for what you're saying is that you're comparing an evaporative cooling system to a heat pump based one, in which case the 'reverse cycle' aspect is not the thing causing the inefficiency.