That might be the case, but it would be worth confirming on your heatpump. The first stage of these inverter based devices is to generate DC so they’re basically a power supply from the grid’s point of view, not unlike what’s in your TV, your computer or your EV. What happens after that (inverters, variable speed motors etc.) is not visible to the grid.
The closest thing to a heatpump that I have handy to measure is my inverter based fridge. It’s a long way from the old AC compressor type fridges that cycle on and off all day. In those you might see a fairly sinusoidal lagging current draw typical of an electric motor.
My inverter based fridge is constantly tuning the power going into the compressor to match the current heat load. Once things have reached steady state it hovers around 30 to 40W from memory. I just whacked it up a notch to make it run hard (a fairly constant 100W) and captured a waveview. You can see it’s a long way from sinusoidal but instead shows a classic SMPS signature:
All those harmonics contribute directly to Irms but add almost nothing to RealPower and since
PF = RealPower/(Vrms * Irms) the harmonics make the denominator bigger and do next to nothing to the numerator, resulting in a rather poor PF of 0.63.
If I drill down to look at just the 50 Hz stuff then it appears as a very slightly inductive load:
Solving that triangle will give you a cos(phi) of 0.974 for whatever that’s worth.
So my fridge demonstrates pretty spectacularly just how different PF and cos(phi) are. People often use the terms interchangeably but shouldn’t.
I think the PF of your heatpump will come down to how much effort they’ve put in to designing a PFC supply in the very first stage, where the DC rail is produced. PFC supplies are very common in datacentres and EVs (you can see some examples here). Working in your favour is that your heatpump likely draws a lot more power than the 100W my fridge draws. Generally, the bigger the power supply, the more PFC effort they put in - often by regulation. Those 11kW power supplies in EVs (7.4kW on single phase) do a spectacular job at looking like a resistor to the grid. Your heatpump power supply probably sits somewhere between there my fridge.