Well sure, if you never spend a little time on improving your mobility and flexibility, but most athletes do incorporate mobility and flexibility work into their training. And for the record, Olympic weight lifters are some of the most flexible and mobile athletes in the world and they lift ALOT of weights.
Griffey generates his power from his lower body and posterior chain, and as anyone can see those parts of his body seem to be pretty well developed. Big guns aren't nearly as useful when it comes to hitting a ball far.
