I think the post is arguing for a superset of the definition of exercise which includes the gym as opposed to a set definition of exercise defined by the gym ex

I think the post is arguing for a superset of the definition of exercise which includes the gym as opposed to a set definition of exercise defined by the gym exclusive of other activities. A superset definition would also include lifting my child for piggyback rides, a brisk walk with a friend, or practicing a flash mob.