It appears to not work on DexNav Pokemon, However.
This is how to catch legendary Pokemon with the right nature in ORAS. Synchronize Pokemon Guide Omega Ruby and Alpha Sapphire – Getting Perfect Nature Legendaries ORAS This is a guide for the Ability Synchronize in Pokemon! Synchronize gives you a 50% chance to have a wild Pokemon have the nature of your synchronize Pokemon. Now, that’s still remarkably rare, but using the Shiny Charm in tandem with the following methods guarantees you’ll encounter a shiny eventually. In other words, your odds of running into a shiny increase to about one in 2,730.
He’ll congratulate you and give you a Shiny Charm, which increases your chances of encountering shiny Pokémon in the wild by 300 percent. After you complete the National PokéDex (that means you catch every single possible Pokémon between every game excluding a few legendaires, a total of 718 Pokémon), you can go talk to Professor Birch in Littleroot. One of the hardest items to acquire in Pokémon Omega Ruby/ Alpha Sapphire is the Shiny Charm.