Buried Treasure spawning without Heart of the Sea

Seed: -8534830376248092263

/tp @s -1015 ~ -1127
/tp @s 5977 ~ -3431

Buried treasure chests are supposed to spawn with one (1) Heart of the Sea item, but it hasn't been happening. 

I haven't figured out yet how the loot table format works, but here is the heart of the sea part from the buried treasure loot table:

{
      "rolls": 1,
      "entries": [
        {
          "type": "item",
          "name": "minecraft:heart_of_the_sea"
        }
      ]
    }

It looks to me like the chests are spawning too full to include a heart of the sea, which doesn't appear to make sense to me since it is at the top of the loot table list.