>I doubt it's that the circadian rhythm is news to the person you're replying to, but rather that that line is fairly badly written, particularly the "want sex and have asthma attacks or a fever in the afternoon" part

That was the best written part of the description, and was written with a clear intention.

The author wanted to add some more surprising (but still really affected by circadian rhythms) stuff, to make the description more memorable and interesting, even to those that knew the "hungry" and "sleepy" part.