Board Thread:Fourth Databook/@comment-24577388-20141105025614/@comment-945885-20141105104012

They don't "all of a sudden" have multiple natures.

We already know that it's common for jonin to be proficient in at least three nature transformations. And that's all they are: proficiencies.

Nature transformation is not some sort of holy grail. We don't need to see every single ability in a character's repetoire to know that they have a repetoire of various abilities. These are things that they've trained in, in order to use them when the need arises.