How silly, with the Society trying to define what level of physical abuse is acceptable, and the level which constitutes "extreme" abuse.
Perhaps the basis of the clarification of policy is NOT unfounded on scripture, and maybe they followed the Bible's approach for disciplining a slave (replacing the word 'husband' for 'man', and the word 'wife' for 'maid-servant'), as found at Exodus 21:20?
21:20 And if a man smite his servant, or his maid, with a rod, and he die under his hand; he shall be surely punished.
21:21 Notwithstanding, if he continue a day or two, he shall not be punished: for he is his money.
21:24 Eye for eye, tooth for tooth, hand for hand, foot for foot,
21:25 Burning for burning, wound for wound, stripe for stripe.
21:26 And if a man smite the eye of his servant, or the eye of his maid, that it perish; he shall let him go free for his eye's sake.
21:27 And if he smite out his manservant's tooth, or his maidservant's tooth; he shall let him go free for his tooth's sake.
So the husband has to be careful NOT to cause the wife to lose an eye or tooth, as the husband then must set the wife free, experiencing economic harm. He also must be careful not to beat the wife to death, for that's considered manslaughter.
However, the law acknowledges that if the wife is beaten and manages to hang on to dear life for a "day or two", then the man must NOT charged with manslaughter, and is off the hook, scot-free, since the husband enjoys the presumption of innocence that the wife MAY have died from NATURAL causes (eg they died of internal bleeding a day or two later: but the beating itself had NOTHING to do with it. Just a coincidence, folks; move along....) Besides, the loss of the wife at the man's own hand is considered punishment enough ("for (the slave) is his, worth $$"). .
So I can see it now: the wife is supposed to jump around to try and align the blows of the husband's rod to knock out a tooth or eye and earn a separation from him, but the husband is trying to land blows on areas that don't leave bruises that confirm any "extreme abuse".
And if the wife IS beaten unconscious, the husband suddenly must administer CPR to at least keep the wife alive for a day or two to avoid manslaughter charges.
So there's your Biblical morality in action, folks. THAT'S LIKELY the scriptural basis used to come up with this policy, defining "extreme abuse" as that which causes the loss of an eye or tooth; only THEN, is the wife "set free" and allowed to get a scriptural divorce. The husband then must experience the economic harm of paying alimony and spousal support, since she is "his money". Lovely, eh?
Anyone who says, "But YHWH is the moral law-giver: we're not required to use man's secular laws" is fooling only themselves.