Many species of worms have been adapting to some very adverse weather conditions for eons.
But you are correct that worms that hatch into a given environment (unless it's very hostile) will tolerate, if not thrive, in that environment where mature worms might have perished. Like us perhaps, getting more set in our ways as we mature (and get that oldfartitis!)
I also believe that redworms reared outdoors are better conditioned to handle wide ranges in temperature, moisture, etc. I have routinely seen very active worms in sopping wet soil at temperatures just above freezing - conditions we'd rarely expose a bin to and expect a positive outcome.

Thanks for the input abbeysdad,
One thing that I noticed about the worms outside and that is how much bigger they are than the ones in the inside bin, although they are definitely the same species.
I guess it's kinda like goldfish - the larger the environment they live in the bigger they get!
It's really good to know that there is hope in turning this 'sand box' of a yard into something that will help plants to grow and thrive.
Janet