This site has not yet been updated to reflect the changes in Reborn v19.5. It still only reflects the state of the game as of v19.16.
If the Pokémon with Neutralizing Gas is in the battle, the effects of all Pokémon's Abilities will be nullified or will not be triggered.
There are no Pokémon with this ability. (It's probably a Gen 8 ability that's snuck its way into the database by mistake.)