It sounds like we're similar. My personal, entirely unscientific self-diagnosis is that I have a well-defined circadian rhythm like most people, but it's easier for me to override by obsessive interest than for most people. Even sans coffee (which I'm pretty careful about as I near 40), if I'm really interested in something, I can work on it in a block of time up to and over 24 hours. Naturally that futzes with my sleep. My "tired-impulse" is relatively weak compared to my "this is exciting" or "people are waiting on this" impulse.

Before I ran a company (about 1/3 of my career), I mostly managed to hold things down on a "normal" schedule, but I was always tired and frequently had performance reviews where the only complaint was my tardiness.

There are some interesting data points: while camping (which I do a lot of -- several weeks per year), I do tend to sync up with the sun, even though in northern Europe that means waking up before 5:00 a.m. There's also limited screen time. (Though I did work from tent on a remote beach in Crete for a month this year.)

I picked up some melatonin tablets in my wife's home country (where it doesn't require a prescription), and will experiment with that in the near future for I-really-need-to-sleep-now times, but as much as my sleep is weird, it's so intertwined with my personality now that I'm hesitant to medicate it away even given the chance.