Seems impossible to increase chance for smooth hatch to give a stone hatch egg

It's been a long time I have build a room for hatches, so that they can product some coal by feeding them with sedimentary rock.

Now, quite all have become stones hatches, which is normal.

But, recently, I got a smooth hatch.

And looking at him, it seems there's no way to increase chances of getting back a stone egg from him because his diet do not include sedimentary rock, even though it's said that if he eats this material, the chances should increase.

He's aged 10 cycles, and is currently hungry because, even if the feeder is full of sedimentary rocks and other critters can get it, this one do not have anything to eat.