If you've done any winter camping, you would know it's virtually impossible to tell if deadfallen wood is dry or soaked when it's frozen solid. Anything on the ground is best assumed wet and left there. There is no "dryer wood inside" of a piece of wet fallen wood on the ground and you don't have the time and energy to waste to get to it if there was. It's one thing to collect and process enough wood to make a small fire for hot cocoa on an afternoon hike, but another thing altogether to process enough wood to keep a wood-hungry open fire going all night to keep you from freezing. In a survival situation, you would spend/waste a lot of your energy, calories and time trying to get a warming fire going with deadfall wood of unknown condition. Even dead standing wood is sometimes soaked and you won't know until you try to burn it and water and steam starts hissing out. To survive in the cold, you need to be as efficient as possible with wood processing, hence the advantage of having the proper tools if possible. Trying to learn survival by theory is risky and mostly worthless. Get out and do some actual camping in the winter and in the rain and bad weather. You can do it very safely, close to your car or home in case you have to bail out. You'll learn the realities, not the theories, and the amount of self-confidence you gain will be great.