How To Fix:

For anyone who has the same issue, the implementation is a bit different now and Mojang has been stingy with the documentation as per usual:

• Category is no longer in the description of a block/item
• minecraft:creative_category now works as follows:

"minecraft:creative_category": {
  "category": "category_name" //can be Construction, Equipment, Items, Nature or Commands
  "group": "itemGroup.name.group_name" //Example would be itemGroup.name.planks for the planks group in construction
}