Structure generating one block in the ground

i genuinely have no clue why it's doing this, heres the structure json
{
    "biomes": ["jungle", "bamboo_jungle", "sparse_jungle"],
    "liquid_settings": "ignore_waterlogging",
    "spawn_overrides": {},
    "type": "minecraft:jigsaw",
    "start_pool": "ddp:jungle_hold/jungle_hold",
    "size": 7,
    "terrain_adaptation":"beard_thin",
    "step": "surface_structures",
    "project_start_to_heightmap": "WORLD_SURFACE_WG",
    "start_height": {"type":"constant","value":{"absolute":2}},
    "max_distance_from_center": 116,
    "use_expansion_hack": false
}