I would guess, that intrinsic factor is tied to the RDA for B12.

Biologically systems don't make "extra"...and only what you need.

So with that basic trait, I'd assume that enough intrinsic factor is made to deal with daily B12 absorption from animal foods.

The only difference is that intrinsic factor when latched onto B12 can work in the presence of food (as it arrives naturally) whereas passive absorption requires an empty stomach for best results. If intrinsic factor is broken, than passive absorption is all we have. Doctors don't even use the Schilling's test anymore to see if it is working. The labs have discontinued it.
http://en.wikipedia.org/wiki/Schilling_test

There is a test for autoimmune damage to the parietal cells in the stomach-- it looks for antibodies to the parietal cells:
http://en.wikipedia.org/wiki/Parietal_cell

B12 cobalamin is a very large molecule, difficult to absorb, so nature evolved this system of intrinsic factor helping because so little B12 is available in each meal.

The MMA test and homocysteine test show if the B12 is actually working in the tissues. The MMA test is specific for B12.
http://labtestsonline.org/understand...s/mma/tab/test