I think you've got most of it
Because daylilies are day-neutral for flowering doesn't necessarily mean they don't respond to photoperiod for other things, though. I'm thinking of things like dormancy, which may involve temperature, photoperiod, or a combination of factors, but daylily dormancy isn't well understood.
Tomatoes are also day-neutral for flowering. What I meant by continuous light damage was physical injury, such as chlorosis, stunting, necrosis (in those plants like tomato that are sensitive to continuous light).
Plants that are not day-neutral for flowering are either long-day or short-day plants. While the terminology suggests length of day, the plants actually measure the length of darkness. Ten foot candles is the minimum you would want to supply artificially from an incandescent bulb to influence photoperiod.
For maximum photosynthesis you'd be looking at somewhere between 500 and 3,000 foot candles, depending on the particular plant's tolerance. Bright sunlight can give much higher intensity than this but going above the plant's upper limit (light saturation point) won't further increase photosynthesis.
