Stony Cliffs Are Cool Worlds you have already played

Because the work happens while land is generated, it applies to terrain created after it is installed. Chunks you have already explored keep the shape and the surface they were born with, so adding this to an existing world will not rewrite the hills around your base.

Walk far enough into unexplored land and the new terrain will generate with stone faces. This also means a world can safely be played with or without it later on - nothing depends on it being present.