After looking at it a bit more, I think I may understand how the rates work now.
The global rate is used for the specified area - in this case, in The Great Crater of Paldea, Roaring Moon and Iron Valiant have a 50% encounter rate.
The biome rate is used globally throughout the map, so:
- Roaring Moon has a 5% chance to appear in a "Cave" biome, and a 1% chance to appear in a "Underground" biome.
- Iron Valiant has a 5% chance to appear in a "Cave" biome, and a 1% chance to appear in a "Underground" biome.
This is so long as you have the flag
FSYS_SCENARIO_GAME_CLEAR
within your save data set to true.
Though, if this is truly the case, that means that the following paradox Pokemon are available before beating the game:
Code:
Scream Tail
Flutter Mane
Iron Jugulis
Iron Bundle
So I'm not sure how accurate that is.