Who knows? It's a mental thing, if you put yourself in that position then you have the facility to take yourself back out if it gets too much so it will never be a proper test of whether you can or not.
Only if you "fail". If you succeed when it is only a test then you can assume you would have survived the same things if it was for real.
When you pull yourself from the wreckage, bury your wife and children and the rest of the passengers on board the plane and then live happily ever after living like a wild man then you would be able to say I did it. For me, bushwhacking is a choice, a hobby and a way to spend my free time. I don't see it as a competition.
The "rest of life" scenarios are rather extreme. Say instead 1-2 weeks, with the kind of kit a normal person might have if they were planning on spending a day watching birds, picking mushrooms, whatever. Clothes, some rainwear in case it starts raining, an extra layer in case it gets chilly. No possibles bag full of goodies, no magic firestarting toys, no knife. If you can survive two weeks under those circumstances you would have survived probably at least 99% of all "lost person in the woods" incidents. The roughest ones I know of that was bushcrafty in nature (i.e. not crawling down parts of Mt Everest with broken legs or swimming ashore after your fishing boat sunk) was a ptarmigan hunter who spent a week stuck in the snow after an avalanche and Slavomir Rawicz and friends walking from a Siberian prison camp to Tibet (assuming that story is not a fake). Most incidents are far, far, less arduous; 1-3 nights out, perhaps minor injuries.
Now we come to
why one should practice for something that one can also ask oneself: "how did you manage to be silly enought to end up there?". For me the answer is that it gives me freedom and confidence. Knowing that if my kit all went away while on a canoe trip (overambitious lining attempt, went on a side trip and a forest fire ate your kit, whatever) I could make it out, knowing that if my tent blows away in a winter storm I can dig a snow cave and live comfortably in it, knowing that if the fae turns my head (of course I could never loose my bearings on my own...) and I get lost picking cloudberries I can just spend the night, and find my way home tomorrow. Knowing that even without a compass I can find north. Knowing how to start a fire even if all my matches are wet and my metal match lost. Knowing that if I go through the ice in winter all is not lost. Most of these things are unlikely to happen to me,
but if they happen I know from experience I can manage.
