Jesus is just wrong. Rock and Troll!
Ty, You will be fine transplanting during flowering if you are gentle. I do it every grow as I sex plants. Usually two weeks up to a month into flowering with no severe problems. It's much easier to do and less damage to root ends if you do it with a moist rootball. Be sure to water in really good after re-potting so no dry soil pockets. I use Superthrive to water in as it really helps against transplant shock. Usually a few days and they take off growing twice as fast. A couple days lost to transplant is much better than a rootbound plant with no yield.