It seems that the bird's egg can break more easily than outside. But it is not for that reason that the little goat costs more to leave outside, but vice versa. By making strong the chito on the strong skin of the interior, the outer shell is cracked and immediately breaks the egg. The participants were researchers from Manchester and New Zealand, after conducting several tests.
To measure the resistance of the outer crust, it was pressed through the inside of the split egg and half plane. To measure the consistency of the inner layer, the egg was pressed on the two outer faces. The conclusion was that the interior surface is 34% firmer than the exterior.
It seems that your explanation may be in the microscopic structure of the egg shell. According to the researchers' studies, the inner layer consists of calcite crystals in the form of hexagon and the outer layer is a network of organic material. It seems that this outer skin weakens the entire structure of the egg.