As I understand it bubble columns cannot form in 1-wide tubes, they require at least 1 adjacent water block to form. if a bubble column is surrounded by regular blocks it will not form at all. Since the new waterlogged blocks count as a water source block in other areas i.e. hydrating farmland, growing sugar cane etc, I expected waterlogged blocks to count as a source block for bubble columns as well.

The Pictures make this clearer.

Steps to Reproduce:

Create a 2x1 by 3-high block tube of glass, or some other block.
Place 1 Soul Sand, or Magma Block at the bottom of this tube.
Fill the entire inside of the tube with water source blocks
Observe that the bubble columns form.
Place a fence or any other waterlogged block (sign, ladder, trapdoor etc.) on the bottom of the tube, next to the first bubble column block above the soul sand.
The bubble column will stop, as if a sold block was next to it.

I would have expected the bubble column to remain unaffected, since waterlogged blocks count as normal source blocks in other areas.

This may be working as intended, but it seems inconsistent with other uses for waterlogged blocks.