I wonder what kind of testing was done for safety.
It seems as if either side cracked, it would bring down the entire staircase.
Since it is 5 pieces laminated, it's like a front windshield of a car: A crack has to go through all 5 layers to have any effect. Otherwise, even with cracks, it still would be safe. Besides: That thing weighs tons. Compared to the weight people add when going up and down, there is not much more stress on it.