>>33309321You're only half right. The problem with the term "Legendary" is that it's been used officially to refer to different groupings of Pokemon at different times.
Prior to Generation V, Legendary and Mythical Pokemon were considered distinct groups in Japan, while the west considered Mythical Pokemon to merely be a subgroup of Legendary Pokemon, generally referred to as Event Legendaries. Starting in Generation V, the west also began to distinguish Mythical Pokemon from Legendary Pokemon.
In Generation VII, the hierachy of legendary Pokemon was explicitly laid out in the game's coding, defining two distinct groups: "Legendary Pokemon", which are banned from the Battle Tree (with "Mythical Pokemon" being a subcategory of this group), and "Sub-Legendary Pokemon", which are not. "Legendary Pokemon" are identified as such both in official media and in the Pokedex and have a gold background, while "Sub-Legendary Pokemon" have a green background.
This would seem to indicate that Mythical Pokemon are once again considered "Legendary", while tjhe minor legendaries allowed in battle facilities are no longer classified as such. However, the GTS option to filter requests for Legendary and Mythical Pokemon notably filters requests for "Sub-Legendaries" as well. Also, an advertisement for the recent shiny Tapu Koko distribution identifies it as a Legendary Pokemon.
What this means is that "legendary" is being used officially in two different senses: the general overarching sense used in the west since gen I (which includes all Legendary, Sub-Legendary, and Mythical Pokemon), and a more specific sense of Pokemon banned from battle facilities (which excludes minor legendaries). Ergo Type: Null, Silvally, and the UBs are just as legendary or non-legendary as things like the bird or beast trio, depending on which definition of the term you're using.
