Adding on to what DrPumpkinz says, the Cloud Nine / Air Lock message can result in information leaks even in modern generations (including Gen 8). For whatever reason, Air Lock and Cloud Nine aren't included like the rest of entrance activation Abilities (e.g. Intimidate or Pressure) to trigger after Ability changes happen (like Skill Swap or Entrainment). You can easily create an information leak like this:
1) Switch in Neutralizing Gas
2) Switch in Cloud Nine
3) Switch out Neutralizing Gas
So Cloud Nine would never activate in this whole exchange, even though after step 3) weather really is being negated. But if you don't know whether or not the Pokemon has Cloud Nine (say Golduck, or a Pokemon in hackmons formats), this would leak that the Pokemon really does have Cloud Nine.
So this implementation would need to be based on revealed Cloud Nine / Air Lock activations.
EDIT: Zarel has since pointed out that this won't be a problem; it will be based on revealed Cloud Nine / Air Lock activations.