Generations III-V
From Pokémon Emerald onward, if a Pokémon with Synchronize is in the first slot in the party (even if fainted) when a wild Pokémon is encountered, there is a 50% chance that the game will force it to have the same Nature as the Pokémon in the first slot.
Instead is counting. When a Pokémon with Synchronize is burned, paralyzed, or poisoned by another Pokémon, that Pokémon will be inflicted with the same status condition. Synchronize will not inflict sleep or freeze.
My question here is, does synch 50% works or not in pokemmo?