Actually the thing that snaps is the spine. So far the description has been contact effective. We haven't actually seen any logia getting hit on the arm and thereby getting the arm dislocated due to the large force; which is analogous to clutch snapping the spine by leveraging the neck backwards.
In fact it appears that Haki only causes damage but the method of contact doesn't accurately depict the damage received. Otherwise some of the logia admirals would have been shattered or lost some limbs.
But if haki is able to extend beyond the body's boundaries and can be shaped, then we could end up with a haki ball that can capture logias
