Feature:
A config setting to Limit MossyStone blocks from 'growing' when beyond set distance from a Water source block.

Alternatives:
Unknown (ProjectE Ring of the goddess uses tick advancing to accelerate growth)

Additional info:
ProjectE ring tick advancing is forcing MossyStone growth slowly converting entire caves.

there is a limit, thats likely the top edge of an aquifer or something.
if not, maybe its having some sort of bonemeal effect that spreads the moss