Actually, I don't think its the ratio of light to dark. They just need 12 hours uninterrupted dark to know that its flowering time. So the idea is you give them 12 hrs dark, then only what they need for light. Or in veg, you know they want lots of light, but only however much dark they need to keep up with the light.
Anyways - there are people who do it. The hard part is getting timers that can do it. I think it yields less, but obviously if you're running an 18-20 hr day you're getting 20-25% faster harvests.
I had thought about it in relation to the controller, since I see a very slight droop of the plants by the end of the day, and a very slight perking up before the lights come on - I fugured maybe someday I'd try shaving an hour or two here or there.