Why aren’t cinderblock basements waterproofed by pouring concrete into the hollow areas of the Cinderblock. The advantage would be that the wall would become stronger as well.
What are CMU’s made from? Concrete. The reason water runs through the CMU is because concrete is porous. Fill concrete with concrete and it is still porous.
And that’s your answer.
There are situations where they require the block to be filled. Not always 100% filled depends on the design and decisions made for the design. Not for waterproofing though.