The point that MD is trying to make is this:

Is the person in IMMEDIATE danger from a condition that they can only be protected from by removing them from the vehicle? If the answer is no, don't bloody move them.

The only time I'd ever pull someone out is if the vehicle was in immediate danger of catching fire or they were about to need gills. And I've had training for vehicle extractions. I don't care if it is getting cold- manage their hypothermia by bringing heat to them, not them to heat. I wouldn't even pull them out if the car was about to go over a cliff- I'll stabilize the vehicle first. There is more to this than just spine issues- a broken rib can puncture the lung or pericardium. A broken femur or humerus can cut a major vessel leading to a internal bleed out in minutes, or sever a major nerve. I don't even care if I can't tell what is leg and what is dashboard any more- I'll get the bleeding stopped as best I can, but I'm not pulling them out, I don't have the proper equipment to extract them without probably worsening their situation. After I get the door open for them (pry bar, not chainsaw), if they can't get out on their own, they are staying there until the guys with the big truck show up. I'll do everything in my power to keep them alive, warm and from freaking out, but I will not endanger someone that way.

You are relying on military training. I hate to tell people this, but there is a lot of times where military training teaches you the wrong damn thing. No one is lobbing HE at you, there aren't snipers about, and odds are the vehicle isn't about to burst into flames- you don't have to pull them out. Dig in, keep them alive where they are, and call for the cavalry. I get basically the same kind of weather you do here, and I know all about places where you can spend an hour or three and not see another car on that stretch of road. You get the stable, keep them warm, mark the position from the road as best you can, and if no one is with you and you can't get a call out, you tell them you are going to get help, make sure they understand that, and you go.