You know something I noticed? And they could break this trend with Gen. 9. Ever since they started adding Pokemon mid-generation with Gen. 7, new Pokemon have come in three groups each time: the first group in the initial pair, which trends to be the biggest, then a group in an expanded version of the initial region which tend to match it's theme (Alola visiting Ultra Space, Galar having big legends) and includes a new mythical (Zeraora, followed by Zarude), and the third and final representing a new feature in a region we've already been to (Meltan and Metmetal representing Go connectivity with Let's Go, Pikachu and Eevee, and newly discovered evolutions of existing Pokemon in Legends, as the Sinnoh region had whole bunch in the initial fourth generation).