Jigsaw Structures With Heightmap Projection of World Surface Generate on Ocean Floor

I am creating a structure that generates on the ocean surface with the Jigsaw Structures Experiment. However, when I set the jigsaw's heightmap_projection to world_surface, it generates on the ocean floor.

Taking what I can from the very incomplete docs, this should generate it on the ocean surface. In addition, there is a separate heightmap_projection for ocean_floor, so it makes sense that world_surface would place it on the top of the ocean.

Steps to Reproduce:

1. Attach mcpack to a Minecraft Preview world with Data-Driven Jigsaw Structures enabled.
2. Locate structure ( /locate structure httyd:dragon_hunter_ship )
3. Notice structure is nearly always on the ocean floor

Observed Results:

The structure is on the highest solid block.

Expected Results:

The structure should be on the highest non-air block, which is water.