Could be. Does your PHEV start moving the same moment your foot comes off the brake? Once it starts moving can you feather the brake, hear is squeak lightly, and the car is still moving?
It seems to me that programming could stop unnecessary power draw at a stop, but besides someone's actual measurement, there are too many other clues for me to think they have done that. Easier to just delete (or give owner the option) the creep function altogether.
In a standard ICE car with a standard automatic, there is certainly a higher load on the engine at full stop in drive versus neutral. Those cars are not efficient enough to be worth shifting into neutral - any efficiency gain is minimal. The same could be said about our cars perhaps (more so for the HEV than the PHEV), some small power drain measured in dozens to hundreds of watts has a very small effect on total efficiency (mpg). But it is not zero, and that has an emotional impact to me. For the same reason, I pay attention to headlight use, and only use it when there is a real safety impact to myself or others. No running lights.
2018 Kia LX HEV Metal Stream with Advanced Tech