my general understanding is that stress in general towards the end of flowering will force extra trichome/resin production, but doesn't provide the plants enough time to turn hermaphroidite. the plant gets stressed out, and tries to protect itself (trichomes are defensive structures). i don't doubt that these methods provide some small benefit to the final product, but i also believe that you can add a lot more potency to a plant by keeping it happy throughout its life. i've also heard of sticking needles/nails into the stems a few days before harvest, dark periods, not giving it any water, and on and on.
edit: i don't think any of these methods will really increase weight in any very significant way, just potency through resin/trich production.