Trying to make multi-layer terrain gen

Attempting to make a (top to bottom) snow -> ice -> deepslate surface terrain gen for a custom dimension but it end up looking like the picture. Relevant:
{
  "sea_level": -120,
  "disable_mob_generation": false,
  "ore_veins_enabled": true,
  "aquifers_enabled": false,
  "legacy_random_source": false,
  "default_block": {
    "Name": "minecraft:deepslate",
    "Properties": {}
  },
  "default_fluid": {
    "Name": "minecraft:lava",
    "Properties": {}
  },
  "spawn_target": [],
  "noise": {
    "min_y": -128,
    "height": 480,
    "size_horizontal": 4,
    "size_vertical": 4
  },
  "noise_router": {
    "initial_density_without_jaggedness": 4.0,
    "final_density": 4.0,
    "barrier": 1.0,
    "fluid_level_floodedness": 1.0,
    "fluid_level_spread": 0.1,
    "lava": 1.0,
    "vein_toggle": 0.5,
    "vein_ridged": 0.4,
    "vein_gap": 0.3,
    "temperature": -1.0,
    "vegetation": 0.1,
    "continents": 0.0,
    "erosion": 1.0,
    "depth": 0.1,
    "ridges": 1.0
  },
  "surface_rule": {
    "type": "sequence",
    "sequence": [
      {
        "type": "condition",
        "if_true": {
          "type": "above_preliminary_surface"
        },
        "then_run": {
            "type": "block",
            "result_state": {
            "Name": "minecraft:snow_block",
            "Properties": {}
          }
        }
      },
      {
        "type": "condition",
        "if_true": {
          "type": "vertical_gradient",
          "random_name": "minecraft:deepslate",
          "false_at_and_above": 350,
          "true_at_and_below": 349,
          "anchor": 300
        },
        "then_run": {
            "type": "block",
            "result_state": {
            "Name": "minecraft:blue_ice",
            "Properties": {}
          }
        }
      },
      {
        "type": "block",
        "result_state": {
          "Name": "minecraft:deepslate",
          "Properties": {}
        }
      },
    ]
  }
}

Version: 1.20.4
Loader: NeoForge