Hey! I'm recommending an edit to the article for Iron Ball. It does not mention that it negates Levitate as well, it only mentions Flying types at the moment. Not sure if this is a mechanic issue on Showdown that doesn't match the base game (unlikely) or if it just needs an updated description.
https://www.smogon.com/dex/ss/items/iron-ball/
Here is proof that it negates Levitate too from a draft league game I saw: https://replay.pokemonshowdown.com/gen8nationaldexag-1310320456-x45ivtnzqvyyu2hcsok9sekr3uoc7gupw
https://www.smogon.com/dex/ss/items/iron-ball/
Here is proof that it negates Levitate too from a draft league game I saw: https://replay.pokemonshowdown.com/gen8nationaldexag-1310320456-x45ivtnzqvyyu2hcsok9sekr3uoc7gupw