The path is actually closed at night. There's a sign posted. I forget the exact wording but it's something like 'Pathway closed after dark". It's located when coming back from DD to OKW, and is just past the SSR turnoff. The parts from DD to SSR are lit enough that you could still use that section after dark.
However, if going from SSR to DD it's much shorter to use the new path that you can follow. (Go up to the quiet pool, face DD, turn left, and you'll eventually find it. It goes to the DD bus stop area.
In any case you wouldn't want to walk the OKW path in the dark, even if you had a flashlight.