I would have thought that the longitudinal fibre alignment of the bamboo tubes would compromise their torsional rigidity .

This is supported by data showing that bamboo has a typical ratio of EI / GJ greater than 8 where isotropic materials with moderate Poisson's ratios (eg metals) give values around 1.3. Since EI / GJ describes the ratio of bending stiffness to twisting stiffness, this says that the bamboo has about 16% of the torsional rigidity of an equally laterally stiff metal tube. Since the bamboo tube will have lateral stiffness less than or equal to that of a metal tube of the same diameter and weight, this gives it at best 1/6th of the torsional rigidity.

It is well known that torsional rigidity of frame tubes is extremely important for handling - you don't want the down tube and top tube twisting enough to pull the head tube out of alignment with the rest of the frame.

Am I missing something or is this another case of something which looks like a good idea but really isn't?