>>34346148From the main Pokemon worlds' perspective: yes, because they are mysterious, powerful, rare, and will only show up due to the actions of Legendary Pokemon (Necrozma or the Cosmog line creating wormholes).
From Ultra Space's perspective: no, because they are ordinary and common.
Marketing perspective:
So far, no, because USUM marketing made a distinction between finding Ultra Beasts and Legendary Pokemon with Ultra Warp Ride.
Game mechanics perspective:
Yes, because they have the same flag as "lesser" Legendaries like the 580 BST trios, the genies, Regigigas, Tapu, and Heatran.