I never found that driving after a night shift was much different to driving after a day shift. Of course, when working nights, I slept during the day. YMMV.
My guess is you've never worked night shift. It's not as easy to sleep during the day as it is at night, even with black out curtain, unless you wanted to get drugged up every day.
That may have been the difference. We didn't get out until 9am (12hr shift) and by then the sun is high and bright so by the time you've driven home you've spent enough time outside where your body has switched from "I'm tired lets go to bed" to "the day is just getting started".
