Does water-proofing have structural benefits in cinder-block foundation?
Surprisingly, introducing water to the CMU will actually increase it's strength because you're providing more fuel for the chemical reaction that turns it from a liquid to a solid. The only time water will cause a structural issue with the CMU is if it susceptible to frost. If you feel the wall is wet on the outside of the building on a regular basis and you live in a region where temperatures drop below freezing then it can cause freeze thaw damage and destroy the blocks over time.

Typically, waterproofing is applied to blocks strictly for architectural purposes. They don't want to allow water in to prevent efflorescence, they want to keep humidity in the building down, or they want to keep actual water out of the building.