I work at a science museum. In our paleontology hall we have a fiberglass ankylosaur. Now, one of those nasty guys is about the size of a baby elephant and has a huge, clubbed tail for whackin'.
It's not a claw, but it is a natural weapon. Should it be used as Finesse? Not logically, no, but since it is considered a light weapon for thise dino (an unarmed, natural weapon attack) plus they may also have Focus and some other things to make them have high bonuses when swatting with it. Let's say the total bonus to hit is +6. Now, if I roll average for him, a 10 on the To Hit roll, that results in a 16.
An average character with DV 13 wearing DR3 armor will be hit, but the armor will successfully absorb some of the blow. Not much, but this whole tail-swatting thing isn't really accurate nor physically capable of getting at weak points in that armor - that's not the point anyway. Besides, it's an animal we're talking about, so cleverly aiming the strike isn't even happening here - the dino simply swings and hopes to roll high.
Now say the ankylosaur rolled an 18 for a total of 24. That's well enough above our character's DR3 armor, so the armor is totally ineffectve and he takes full damage because of the rules for Finesse weapons, which unarmed attacks are by the rules.
Now, go back through that example, substitue any animal and any natural unarmed attack they might have. Works in every case.
With an AP, the has a chance to reduce armor effectiveness if that AP is equal to or greater than the DR of the target's armor. AP1 is practically useless. Why have it if the animal could instead have a high chance to hit, use the Finesse Weapon rules and ignore armor altogether? Makes very little sense.
Look up a Jaguar or a Lion and tell me what thier bonus to hit with thier claws actually is.