That is a great question. People with insomnia or who work night shifts might have altered cyclesI might be misremembering, and of course would defer to you (you being an endorcrinologist..), but I feel that I remember reading in medical school about the cortisol cycle being the least affected by behavioral changes in sleep-wake of most the diurnal cycles.
I think the question is more so of "how does the body know what time it is?". If someone sleeps 11 am to 7 pm, it would be really interesting for cortisol to still be highest at 8 am.