I know people who really need to get up early because the morning is their most productive part of the day by a really huge margin. They start yawning around 1-2 pm to really drive the point home. Their circadian rhythm seems heavily stacked towards the early game.
I work night shifts, some of the early birds are insanely dumb after 3 am, insanely dumb compared to who they are the rest of the day. I see one student of higher education put down his a tool and turn around for 3 seconds then panic wondering where they put it. Not one time! I see him do that hundreds of times. I keep a mental map of where I see him put stuff so that I can remind him or answer when asked. They had plenty of rest, they work hard. It's supper funny to me because I'm a bit like that before 11 am. I'm physically there, if someone asks me to do something my mind makes a raw audio recording of it that I often revisit later to parse out what it was they actually said. In school I've aced tests with 100% questions I consciously knew nothing about. You have to picture it, its hilarious, I read a question about a topic I've never seen before, 5 seconds later I apparently know the answer to the question. I know the difference in file format, recalling unparsed information comes with a lot of irrelevant data about the moment the teacher explained the topic. After 1 pm I only retain the relevant parts, those files contain almost no information about when I learned it, their attachments are my own thoughts.
Of course at times I have to condition myself for morning productivity, I can for example get up at 4 am if I need my brain at 9:00. I can go to bed early, at exactly the same time, rest the body/eyes and think about life for a few hours. It works but it feels wrong, it screams wrong.
I did a hilarious experiment one time where I went to bed at 17:30 straight after work and set the alarm at 1 am. It felt perfect but had negative social implications.
Maybe its a cool idea for a startup. It seems one hell of a perk from my perspective.