minecraft-assets/data/minecraft/worldgen/configured_feature/birch_tall.json

{
  "type": "minecraft:random_selector",
  "config": {
    "default": "minecraft:birch_bees_0002",
    "features": [
      {
        "chance": 0.00625,
        "feature": "minecraft:fallen_super_birch_tree"
      },
      {
        "chance": 0.5,
        "feature": "minecraft:super_birch_bees_0002"
      },
      {
        "chance": 0.0125,
        "feature": "minecraft:fallen_birch_tree"
      }
    ]
  }
}