Blocks placed with the simple_block feature type aren't consistently waterlogged

Whether a block is waterlogged or not when placed from a simple_block feature type is inconsistent.

Steps to Replicate

• Download bug-report.zip, which is a datapack that overrides the seagrass_river placed feature and replaces it with a feature that places an oak slab.
• Create a world (seed doesn't matter, image attached uses seed 0)
• Go to a River biome
• Take note as to whether or not the oak slabs are consistently waterlogged. You may have to travel a small amount to find inconsistencies.