For a long time you couldn't even build herbalists in all cities, yet no one else has found issue with this science. The policy is fine Stoneworks are pretty situational, have been forever, I don't see a sudden major issues (it was still situational when it buffed forests too). We could just ban herbalist without jungle, but now you are being foolish. If it needs to be banned, just don't build it (how is this not a solution?) If I recall correctly, we cannot have herbalist dependent on jungle or plantation, which is why its just available everywhere.