The Rope used for grapes in Rustic acts as a barrier to the water from the sprinklers.

This actually makes total sense in a minecraft way, however it would be nicer if a piece of rope didn't prevent irrigation. ^_^

I'm going to say that we won't fix this for now, since as far as I know there is no way of telling if a block is solid in a direction or what that even means. Would it be considered valid to water through something like energized glowstone? Sprinklers water down, and can only water through air blocks. This would be one where we'd need to come back to it and make JSON files describing "air" blocks, which seems to overcomplicate things too much.