as a collective of people who deal with imagery, it's often more telling to see a picture, than read a chart.
I agree the the final arbiter is the human eye.
However, it's my experience that the human eye is not necessarily a good judge of absolute values such as exposure or Signal to Noise Ratio (SNR). In this case I offer the chart as "confirmation" that what the eye judges seems reasonable. Had it been otherwise I would be questioning why; as I trust the measured data more than the human eye.