I can't say your experiences are wrong, but it seems to me that by stretching you would get roughly the same amount of weed, just spread out farther. By not letting it stretch I would think that you are able to keep the light closer to more parts of the plant instead of mainly the tips, thus likely increasing your yield. Now just because I haven't heard of stretching in flowering, doesn't mean it aint a good thing. There's a lot for me to learn yet on my path to knowing everything. Perhaps somebody could try a side by side test sometime. Hey wait a minute, I am somebody.