If you flush at the proper time there is no yield loss. If your buds are still swelling, they arent ready to be flushed. If you have properly fed your plant up until flush, there will be plenty of nutrients stored in leaves to feed them what they need. If flushed properly the leaves will be turning yellow 2 days before cut so only 48 hours of "unfed" buds that stopped swelling several days ago.Just by experience, im going to tell you now that flushing organics is a bad idea,when you flush organics not only will you take a yield cut,the bud actually wont come out as good either. Try it for yourself or save your time and forget about flushing. If you have ever grown in organic soil you will notice the plant will automatically use its stored nutrients towards the end of flower naturally no flushing needed.
But I am all for people growing however they feel best. So to each their own.