I've always considered it this way if you do something like rotate the tyres on a car to equalise wear you are swapping something over because all the components in the set remain the same they're just moved about. If however you're replacing something with a new component from outside the existing set it could be seen as swapping out. I suspect some people use Swapping out where Replacing would do. To me swapping out implies It, whatever It is may be used somewhere else rather than simply get binned.
This however may be semantic gymnastics and complete cobblers.