I dont think it matters so much when someone starts and is purely a matter of preference.
What does matter is “start windows” where your time is say 5am but the firm has a two hour window either way or something like that. That is when the body doesn’t know what’s going on.
I start at 1am. I love it. And it’s 1am on all my working days, never changes. Not everyone’s cup of tea sure but having that fixed start time I know when to go to bed, how much kip I need etc etc etc