"In this instance, the object is a man, and you will most likely want the pivot to be right at this feet so that you can place him on the ground properly."
That isn't necessarily desireable. Doing so would make placing the character at the correct height easier but would complicate collision detection (since as you even point out the collision sphere is centered at the pivot.) Placing the pivot at the character's feet would mean half the collision sphere is below the character. This is why many games use an extra root bone to determine what height the character should be placed at.
That isn't necessarily desireable. Doing so would make placing the character at the correct height easier but would complicate collision detection (since as you even point out the collision sphere is centered at the pivot.) Placing the pivot at the character's feet would mean half the collision sphere is below the character. This is why many games use an extra root bone to determine what height the character should be placed at.