Lava casting cobble doesn’t really make sense to me since you can get a stone pick very easily, mine in bulk and place in bulk and be done faster i think. No need for iron even.
And smooth stone generator requires placing water sources which makes it even slower than cobble generator. And mining natutal smooth stone is faster because you mine it faster than cobble and there is no delay between blocks, like there is in generator. The difference is small but still there.