Not sure where you read that Yooper, but that is something I would probably question. I did read (think Hackerman posted it) that clones root better with 12/12 light than 24/7, but I don't think it meant taking clones during flowering. As we all know there is a lot of misinformation out there.
There IS a reason that we take cuts in veg rather during flowering. When plants go into flowering, they secrete a hormone that tells the plant to slow down growth and start concentrating on growing flowers. To get a plant that is in flowering to root, the plant kind of needs to change directions--stop producing the flowering hormone and go back into the growth stage. If flowering has not even started, the plant does not have to do this about face and revert back to the vegging stage. All of us that do clone know that cuttings taken during veg root easier and faster than when taken several weeks into flowering. I like to take the cuts a week or 2 before they go into 12/12 in case I lose them, I can take some more before she gets too far into budding. Cuts taken up to 2 weeks in flowering usually root fine, however if they do not take, it will be a lot harder to take cuts from say 4 week flowering plants and get them top root.
Cloning is a great skill to learn and master though. There are many different methods. You will probably have to experiment some before you find the method that works best for you.