Water created by a soul sand/magma block's bubble column does not update after removing the block

The bug

While attempting to confirm MC-126878, I discovered that after removing the soul sand block in the 3x3 waterfall the water does not fall down until updated.

Steps to reproduce

1. Follow the steps in MC-126878 until step 2
2. Remove all of the blocks under the soul sand/magma block and go underneath it
3. Break the soul sand/magma block and see the water not updating properly.