Certain games do have "content pack" DLCs like that though. I remember "horse armor" being somewhat of a running joke when DLCs were a fairly new concept because the game "Oblivion" released a DLC merely containing visible armor for the player character's horse.

I'd say loot boxes are closer to Magic booster packs than what the document describes as they both contain random content and may yield duplicates of what you already have, whereas the document describes themed sets of items and cosmetics. This is closer to the DLCs from publishers like Ubisoft that typically contain a small set of mostly cosmetic extra content and maybe some related side missions.