Seeing how the generator will just be standing in for utility power I don't see how the heat pump would act any differently when on generator then on utility power.
Let us know if you find out anything different.
This is the answer. Everything downstream of the transfer switch won't know what is feeding it.
I deal with industrial and commercial sized uninterruptible power supplies for a living and we interface between utility and generator power using transfer switches all the time, the load doesn't care in a properly setup system. Just match voltage, frequency and phase rotation, if three phase, and you are good to go.
