Lava flows over water plants without any reaction

The bug

Lava flows over water plants without any reaction.

Steps to reproduce (example seagrass)

1. Create a hole two blocks deep. (Using glass will make this more obvious)
2. Place a seagrass at the bottom.
3. Place a bucket of lava on top of the seagrass.

Expected behaviour

The seagrass is either destroyed, or is turned into stone by the lava. Alternatively, the lava is turned into obsidian because it touches water.

Observed behaviour

The lava reacts as if the seagrass were a solid block, and nothing happens.

Affected blocks

All affected water plants:

• Seagrass
• Tall seagrass
• Kelp