The bug

The function apply_bonus takes an enchantment and some parameters to increase the item count of a loot table entry. This function is used in various vanilla block loot tables.

However it appears this does not work for entity loot tables although the enchantment context is still available, proven by the usage of the looting_enchant function, used in almost every mob loot table. This is inconsistent and no warning is given in the log it looks like there is now a warning.

How to reproduce

1. Download and /reload the attached data pack
2. Summon a mob with this loot table

   /summon pig ~ ~ ~ {DeathLootTable:"mc-169473:a"}

3. Kill the mob with a normal sword
    Exactly one diamond is dropped
4. Resummon the mob with the command in step 3.
5. Kill the mob with a looting 3 sword
    Only one diamond is dropped, while you would expect 6.5 on average 

Example loot table

{
  "type": "entity",
  "pools": [
    {
      "rolls": 1,
      "entries": [
        {
          "type": "item",
          "name": "diamond",
          "functions": [
            {
              "function": "apply_bonus",
              "enchantment": "looting",
              "formula": "binomial_with_bonus_count",
              "parameters": {
                "extra": 10,
                "probability": 0.5
              }
            }
          ]
        }
      ]
    }
  ]
}