He did specify that the input pins were grounded. In real life, simple chips like this tend to run the input stage at high currents, which skews things towards low voltage noise and high current noise. So if the input were driven from a reasonable non-zero impedance, or just left open, there would be a bunch more noise.
Amplifiers with grounded input pins tend to have a bad s/n ratio, especially if you measure it in dB.
I wonder what's the absolutely worst noisy amplifier thing around. I recall seeing opamps that ran over 100 nv/rthz somewhere.
John