Actual Experience Driving in the Winter

I live in Canada and winters can get quite cold (we've been getting -30C nights lately). My experience with the Prius is different than the documentation. I have a 2024 Prius Prime XSE.

Engine (ICE) is said to come on if it gets to -15C or colder. In my experience it seems to come on at -12C or colder. I'm going by the temperature on the car's display. I've even had the engine come on a couple of times at -7C, still puzzled as to why that was. Today I drove to work and my car said it was -12C, the engine came on near the end of the 10 minute ride. Driving home and then back at lunch the car said it was -11C and the engine did not come on.

When this happened I was driving WAY below 135Kmh, I did not have my front defrost on, nor was I speeding up very fast. I'm not sure if there are other criteria for kicking in the ICE.