I would recommend that you do a search on "heat treating". You will find a lot of useful information here and on the TG website. But to answer your question directly, the heat treating (commonly called flame tempering) of bamboo flyrods is done primarily to gain speed and some stiffness to the action. The High heat needed to temper the wood should not be used to dry culms or lams. Flame tempering works with some wood species better than with others. Bamboo, Ash, Maple and Black Walnut will flame temper quite well. The same tempering results can be quite desireable in archery. Ancient archers have used heat tempering succesfully since the dawn of the sport.