The Hyundai VP on the video is speaking imprecisely and you may be over interpreting his comments. The Ioniq hybrid’s 12v battery has its own dedicated physical cells in the hybrid battery pack assembly and it is electrically separate from the main hybrid cells. It is not literally using “any one of the LiIon battery’s sub-modules”.Ok, so you were right, they can apparently use any one of the LiIon battery's sub-modules to power the low-voltage system when the car is off. The video here explains it. I suppose that means, however, that the car most likely cannot provide a jump start to another car with a dead 12V (hybrid or not), whereas our Volts could jump start another vehicle if need be.
Here’s a good overview from Car & Driver: