Hum. That would appear to be one of those glitches.
King Meteor isn't on Gym Island, so that's one question down. Using Rock Smash on the rock under the dock at Dewford (if that's the one you mean) should trigger a wild battle with Roclobster. The Stadium, unfortunately, will never open. Regret, didn't catch.
In other news:
POKéMON KERATIN IS HERE!
Click here for the thread of the sort-of sequel to Snakewood - the one that's fully free of bugs.
No no I mean the Gym leader who's a rock. Leader Un-something. His gym is the one with the invisible walls.
King Meteor isn't on the island? K. I got teleported back to Madio caves and saw a bunch of dragons off the side of the screen so I figured I was supposed to go there. My bad. Also YAY will definitely be checking out Keratin soooner rather than later.