Stonghold doesn't generate cut-off in flooded caves/oceans

See title and image. It's a complete wall, ceiling and floor, while it should be cut off like with non-flooded caves.

Seed: -1681023348413992357

/gamemode spectator
/execute in minecraft:overworld run tp @s -20936.55 24.41 -1677.60 326.68 37.16