Internal Observer Effect (Celestial flubbing)

There's a big reason why blunt weapons are so rare. Clothes, nearby air etc. can be claimed, but this can be wrestled away with varying difficulty. One's physical body can generally be considered an 'absolute' claim, essentially inviolable except under very specific circumstances (almost all of which require consent). Lack of outside observation within this closed system essentially allows the soul to fudge things within its body, shifting odds dramatically in its favor to survive a lot of trauma with far less damage than expected. This effect falls apart if the wound is exposed to air (visible, observable), or a body part cut off entirely.

In humans

Celestial flubbing actually plays a part in pregnancy- the carried child counts as 'internal' (even after gaining its own soul), so its characteristics can be influenced in the womb. Doesn't really occur on any practical level with most people- the level of energy investment to create tangible differences is more than most mages throw around over the course of their entire lives.
Cotd are an exception to this, seeing as their children expend massive amounts of soul energy in order to stabilize their existence, so they're all significantly influenced by Celestial flubbing. This is the reason behind their stereotypically 'perfect' appearances. It is also a key factor in their massive infant mortality rate, as flubbing too much often results in a child that cannot sustain itself once exposed to the world.

In Ghouls

Ghouls are an extreme case of this effect: they lack most vital organs entirely, often thought of as consisting only of flesh, blood, bones and nerves internally. They literally exist through flubbing, and their physical bodies would collapse into a pile of flesh if not sustained by a soul.