in today's society it has become moot with all the stimulants, caffeine addictions, crazy schedules, working 2 jobs, sleeping a few hours, etc.
but if we are going to talk actual science first thing in the morning your ardrenaline and hormones are sky high. that is true of any animal on earth who sleeps at night and wakes up to start their day. if you watch the behavior of your own cats and dogs you will notice they sleep then wake up and are very active
there is a reason road races and triathlons start at the crack of dawn and not at 6pm at night
of course the way most people are addicted to caffeine/coffee they aren't tapping into their adrenaline anyway, just like many are on TRT and don't produce their own hormones too