Its based on an OLD statistic/study. One from when cargo TRULY was all night flying. Vs the shift that happened 20+ years ago where a huge portion is day time flying.

People now just like to spout it off to pretend like they know more than everyone else/justify where their choice was better, etc.

I know junior guys at both purple/brown that can hold mostly day, PM, or non circadian rhythm swap schedules.

Our days at the regionals could be more punishing than what they fly.