Attempting to use item tags as a recipe input will result in the recipe appearing in the book, but the recipe will be extremely buggy when attempting to craft it. If the player has the item set as a tag and has everything else, they will simply not be able to craft the recipe, but if the player does not possess the item but does have everything else, it will crash the server and yield the following to the console:

Steps to Reproduce:
1. Turn on your server
2. Join your server
3. Craft the custom recipe that utilizes an item tag
4. Crash

Observed Results:
You are not able to left click to craft the item, and shift-clicking places the item in your inventory and crashes the server

Expected Results:
You are able to craft the recipe with no issues; the server does not crash.

This is not an issue in normal Minecraft worlds that are ran with this Add-on applied; you are able to craft the items as normal with no problems.

Recipe File:

{
  "format_version": "1.12",
  "minecraft:recipe_shaped": {
    "description": {
    "identifier": "lzrd:superstar_boots"
    },
    
    "tags": [ "crafting_table" ],
    "pattern": [
      "X#X",
      "X X"
    ],
    "key": {
      "X": {
        "item": "minecraft:wool",
        "data": 12
      },
      "#": {
        "tag": "lzrd:elemental_shard" //The "Water Shard" item has this tag in it's file
      }
    },
    "result": {
      "item": "lzrd:superstar_boots"
    }
  }
}

Further visual proof in Attachments.