When an interior drainage system is installed properly by trained professionals, the Blocks are all drained permanently by drilling holes into the cavity allowing water trapped inside the block cavity to drain out into the system. These weep holes are then covered by some kind of attached wall membrane that guides the water down to the drainage system. This will preserve the blocks by not allowing water to sit in the cavity. Also the blocks themselves dry out,  stopping the transfer of moisture to the finished wall in front.