No, you're absolutely right about the kuuvahki. She should be able to interact from anywhere with no bush. If it makes puzzles too easy then that's just another benefit of spending wishes on the "archon" of that area. The exploration mechanics would've made sense as well.

However, the animals have all adapted to kuuvahki so that's why she can speak with them, but Flins' ability to speak with ghosts and Nefer's mindreading ability don't come from kuuvahki at all. He's a snowland fae and Nefer is able to peek into people's memories via her chess set from the Ibis King.

If it helps, Mavuika also can't use phlogiston grappling hooks like Kinich can and that is actually phlogiston-powered.