Except they’re two different items with two different recipes. Being said I can’t really expect a Barding made with BfA materials to work in an expansion that is not BfA. The icons are the same, but the tooltips, materials, and spell IDs are not. 324735 is the spell ID for for the SL Barding, 168419 is the spell ID for the BfA Barding.
I just found out about the Shadowlands and BFA ones both having the same ID last night, because I do gold making. I have a crafting operation using Tradeskillmaster with only the Shadowlands one to be made when needing to restock, but the task list keeps telling me to get BFA mats instead of the SL ones. This same ID number makes it a little frustrating.