Like you shown us in that video, it's during broad day light, probably peak daytime hours, compared to a night race. Like I said though, we've never had to encounter night racing/cold temps in game whatsoever, its even labeled in the loading menu that night racing will effect grip.
As for the cars losing traction on and off throttle, I somewhat disagree, yet still, it's what happens in real life anyways, so what exactly are you talking about? I have plenty of cars that grip the road on throttle, as well as off. I agree with you somewhat, that the game does not 100% simulate real life, but at the same time, the things you bring up can seemed to be explained with logical explanations so far.