I have a screen recording on my MacBook Pro, I can confirm. All other multiple word paintings have a space, while this one has an underscore and is capitalized.
How to recreate: (You need to be on xbox series x/s preview)
1. Place the full netherite armor set in your inventory
2. Place a smithing table
3. On the smithing table, put in redstone dust, any netherite armor, and coast armor trim
4. Equip the armor
You should see blank null textures appear when going into 3rd person.
I'm having the same issue.