>>51232621It does because of context. Rotom doesn't know how to speak, that's the point. The whole reason it speaks is because of the Pokedex and the smartphone it resides in, not because it can actually speak. If you notice the vast majority of the limited times Pokemon talk all mostly involve telepathy, possession, or the use of items (phone, z-ring and the pokedex), not the Pokemon physically speaking.
In the games Pokemon are shown to at least be able to understad, or at least trained to, say a few words but the way they're written like here, or Oranguru's "Gu do it, "foryu" or Mimikyu's "Me... Me curse you" seem to imply that Pokemon are not quiet capable of talking, only in a very limited capacity which amount to a few words. So what we have is that from our limit pool of talking Pokemon in both the games and the anime external sources are used for communication rather than direct communication. In this case Rotom using external sources to communicate is distinct from what Meowth is capable of, the audience knows Rotom doesn't normally speak without the aid of technology and it also fulfills a specific niche of taking the role of a pokedex and a smartphone, quiet different than just having any old Pokemon freely talk.
Maybe that's why only Meowth is the only one allowed to be a recurring talking Pokemon and no one else, maybe they don't want to give the impression that it's possible for Pokemon to learn how to talk, and that possibility has been made shot down in the games thanks to LGPE and Yellow shredding Meowth's backstory. Rotom occupies a niche where talking doesn't doesn't obstruct anything especially when the only reason it talks is because of technology. And as the guide says other talking Pokemon are mainly there due to special storylines, and as it states they are very limited. This even applies in the games where the only actual Pokemon with dialogue have all been legendaries and in the case of Zoroark a means to showcase it's illusion powers.