There are two different possibilities here. One is that you came to a full stop hard, or a slow stop and then depressed your pedal a little harder. Both those cases will engage hill stop and delay releasing the mechanical brakes. The other case happens to me often as my driveway is inclined, and often my garage door doesn't open fast enough. So as I'm slowing gently, if I have time, I take my foot of the brake before a complete stop. The car continues to stop as gravity is still working, stops, and then creep starts the car up the incline and into the garage.
This second can be explained by just physics and a steady state creep (momentarily, the braking deceleration and gravity overcame the creep). I didn't explain this earlier as it is a little complicated and as we don't know for sure exactly how the creep function is programmed, this is confusing. It took me a long time to wrap my head around it and separate the braking functions from the creep.
The authoritative post about creep power draw at a full stop has pretty much convinced me. At least enough to shift into neutral at stops that last more than a few seconds! For a lifelong owner of cars with manual transmissions, I find that an easy habit to fall into. I like being able to take my foot off the brakes at stops, although this car rolls so well, I have to stop on a nearly perfect flat spot to take my foot off.
Oh, just thought of one more way for anyone to confirm power draw at a stop. I've posted this before on other threads. At a stop with your foot on the brakes, shift into neutral. And back into drive. You will feel the car's attitude change with each shift. Proof positive of energy consumption!
2018 Kia LX HEV Metal Stream with Advanced Tech