The bug

Custom recipes for items with existing recipes don't stack with the original.

Recipes like purple dye can display different recipes for making the item. I added a custom recipe to make 4 normal chests out of 8 logs (any type) and it made a separate recipe, while I think this should stack with the original one.

How to reproduce

1. Create a custom recipe
2. Mine looks like this:

logs_to_chests.json
{
    "type": "crafting_shaped",
    "pattern": [
        "###",
        "# #",
        "###"
    ],
    "key": {
        "#": {
            "tag": "minecraft:logs"
			}
    },
    "result": {
        "item": "minecraft:chest",
        "count": 4
    }
}

   3. Add it inside a data pack to your saves folder
   4. Load the data pack
   5. Craft the original and new recipe in a crafting table.
   6. Open recipe book in a crafting table