As games get updated, sometimes features are removed, or become redundant, especially with games that cannot have previous versions accessed, like the leaves in Pokémon Go.
Questions like this, while still interesting, are no longer relevant, or useful, as they are not (currently) part of the game anymore. While yes, there is every chance they may be brought back, there is no way of knowing without Developer Knowledge.
In my mind, this situation is fairly edge case; new users may get confused as to its relevance.
So some ways we could deal with it:
- Simply state that this feature is not longer part of the game.
- Protect the question to prevent new users adding answers.
- Close the question for Mod reasons.
IMO, the first option seems like the most appropriate, but that is only in relevance to this particular question. Others may need to be dealt with differently like, perhaps the Diablo 3 auction house questions.