What the parent comment neglected to mention is the working temperature of the gas / fluid in the heat pump.
R410a boils at -48.5 degrees[1]. So based on the size of the system and some maths I couldn’t explain so I’ll hand wave away, there’s your answer. Sorry, that’s the best I can do, you’d have to read some Wikipedia entries to get a better understanding.
Modern heat pumps / AC can be up to 1:4.5 thermal efficiency, but it depends on the the temperature difference, the size of the system, and what you’ve got it set to.
Other places I’ve lived it gets to 48 degrees outside and you set the AC to 17 degreee because Australians are really bad at insulating their homes, so a 31 degree temperature difference, so in that sense the parent comment is flawed.
Also the sun will be adding some amount of heat during the day, which helps in the cold but makes the situation even worse in the heat.
This argument seems flawed. You don't cut the heat off every night and let things cool back to ambient. You maintain a stable temperature.