All natural hides have pores.

Waterproofing functions by obstructing the pores thereby preventing any liquids from permeating the leather.

Waterproofing agents typically contain beeswax and or other sealants.

So where does all that cat urine go?

More often then not the cat urine will find its way thru the stitching and creases penetrating the leather upholstery from these very difficult to clean access points.