That's not definitive. Cortisol and Melatonin are opposites; more of one reduces the other and vice versa.
In the short term, supplementing melatonin to reduce high nighttime cortisol and to get some good sleep in before midnight seems to me like it would outweigh any "likely" disruption in normal hormone patterns.
Trust me, the cancer-causing and downright debilitating (World Health Organization says this, so it's not "likely") effects of high nighttime cortisol are much more dangerous than 6-12 mg. of over-the-counter melatonin every night.
I don't think the people on this board realize how dangerous high nighttime cortisol is.