>>34274542Check the twitter of that famous dataminer, i'ts basically the OP pic. Mythical are event/gift only pokemon (yes, Ash-Greninja counts) and even if you can get infinite of a mythical (like breeding Manaphy or own tempo Rockruff) you still need an original mythical to start the breeding or a friend for trade it to you so they are still special. The dataminer also confirmed the new USUM pokemon as legendary-mythical (Zeraora) and sublegendaries (Poipole-Naganadel, Stakataka and Blacephalon).
The legendary-mythical pokemon are nothing but what the name implies, mythical pokemon that happens to be legendaries too