Mobs can spawn on mangrove roots

The bug

Mobs can spawn on mangrove roots, though they don't spawn on leaves, which behave similarly. This did not occur in 1.19 Pre-release 2, but started occurring on 1.19 Pre-release 3.

To reproduce

1. Create a single superflat world with a layer of mangrove roots on top.
2. Set time to night.
3. Notice how mobs start spawning on top of the roots.

Code analysis

Code analysis by SchimmelGelenk can be found in this comment.