It seems that somewhere during the ATT upgrade to Dragonflight, the Dustbringer was moved to be under the Crafted Item category (Previously this was located under Professions > Fishing):
https://www.wowhead.com/item=44505/dustbringer

I think it was moved in an error, as it is not craftable at all and still remains a fishing drop from Northrend schools

This is the correct location and was moved intentionally.

@DFortun81 cheers, could you provide some rationale for this change, as I am curious to know the story behind it

Sure, on Retail the Professions section has been stripped out in favor of having the organization of Profession data contained within their dynamic categories and the Profession List. These elements show the full nested hierarchy of where to look in the addon. For Fishing, the current standard is to show all of the fishing related goodies that you can acquire through having the Fishing profession as a Crafted Item. A Crafted Item by definition is something that you can acquire by means of a profession and due to the vast number of zones that can be involved with each fish, etc, it was decided that it was appropriate for it to appear as either a World Drop or as a Crafted Item. Since it doesn’t actually drop from a kill, I opted for Crafted Items to be the most appropriate considering the deprecation.

In some cases it might be appropriate to move a Fished item to their respective zones, but for consistency with other fished items that exist in the section already, I believe the intent is to keep it where it is currently.

That said items with exactly one Fishing source zone are generally placed in that respective zone

Just think of something gained by using a Profession as 'Crafted' regardless of if you are crafting with Blacksmithing or Fishing with Fishing or harvesting with Herbalism...