Pokemon Scarlet and Violet files no longer list the Ultra Beasts as sub-legendaries, the internal language used by Game Freak to designate certain Pokemon that exist within the legendary spectrum. As many fans know, for example, all Mythical Pokemon are legendary, but not all legendary Pokemon are mythical. And there are Legendary Pokemon who are not on the same level as box mascots. This change could indicate a major change to Ultra Beasts when they officially arrived in Pokemon Scarlet and Violet DLC.
It's also worth noting that, since launch, Pokemon Scarlet and Violet's Paradox Pokemon were not listed as sub-legends either. This could mean that, on the flip side, Game Freak is moving away from this designation internally, as Ultra Beasts were considered legends in the past couple of gens. They appear alongside legendary Pokemon in Pokemon Sword and Shield's Crown Tundra DLC, after all.
Either way, investigating the Paradox Pokemon's internal classification led Twitter user Kurt, as seen below, to discover that Ultra Beasts were not sub-legends either. They speculate this could be indicative of DLC, as Ultra Beasts are considered "common in another world." It does seem unlikely that fans will travel to Ultra Space in full in Pokemon Scarlet and Violet DLC, which could explain this, as they would be more common there. However, they are perhaps the most solid thing to appear in DLC. When players complete the Gen 9 Pokedex, they are rewarded with a Beast Ball which, as of this writing, has no real use in the game.
It may be wise to see how the Ultra Beasts are described when they are officially added to the game, as this internal language shift could happen for any number of reasons. And no matter what, Ultra Beast is a special designation in and of itself, as these creatures are always endgame-level content and have special parameters regardless. Many fans were quick to point out that Pokemon GO doesn't treat Ultra Beasts as legendary either, since the game's internal legendary search doesn't populate them, but that's not exactly hard evidence either.
Either way, while exact details still need to be ironed out by Game Freak and The Pokemon Company, fans can reasonably expect a DLC announcement sometime soon. Pokemon Day in February is speculated to be the most likely time, and the new games could receive two just like Pokemon Sword and Shield. Many fans want more convergent lines, Paradox Pokemon, and story developments, but it's basically confirmed they'll get Ultra Beasts in Pokemon Scarlet and Violet DLC regardless.
Pokemon Scarlet and Violet are available now, exclusively for Nintendo Switch.