Well, I completed all 242 Pokedex entries and got the Shiny Charm. I’m already seeing the charm’s effects but it’s not applying where I expected it to. I’ve seen seven Shiny Pokemon since I got the charm and only one was from a mass outbreak (Qwilfish), the other six I’ve encountered (a third Geodude, an Alpha Golduck, Buneary, Chatot, a male Combee, an East Sea Shellos, and a second Aipom) have been “normal” encounters.
Did you get the Shiny Charm after catching Arceus and reporting to Laventon? I’ve been hearing mixed reports about Shaymin and Darkrai being required for Shiny Charm eligibility.