Sno-Seal Original Beeswax Waterproofing protects leather from rain, sun, snow, and salt. The beeswax formula dries to a solid wax that "stays put" in the surface of the leather so it lasts longer.
Other greases, oil, and animal products are able to migrate through the leather till they clog all the pores. These waterproofing products fill the natural spaces that are supposed to absorb perspiration and insulate.
In addition, animal fats weaken and rot leather. The tannery worked hard to remove the fats and preserve the leather, so it's hard to imagine why you'd put it back on.
Sno-Seal will help you feel more comfortable in Gore-Tex fabric lined boots because it allows the Gore-Tex-absorbed perspiration to escape out of the leather.