Isotropy of sarcomere bands in skeletal muscle cells
This is sort of technical answer, but I hope its helpful I hope. 

All these bands in the sarcomere are anisotropic.  Isotropy would imply that the structure/properties of something is equally ordered or coherent in all 3 directions.  The sarcomere has definite structure along its longer axis so the H band is anisotropic.  

Since the H band is a small structure compared to the actin and myosin components of the sarcomere, much of the signal that one measures via diffraction or polarization experiments is from those two fibers and less information would be discernible from the anchoring portion (H band) of the myosin filament.  

In the case of the A and H bands, which are identified by electron microscopy, the structure along the sarcomere axis is not very strong - they are thin sections of the sarcomere and tend to function structurally to connect the actin and myosin axes.  

Because of this the information that you might get from A and H band segment studies will be that 'these bands are not very ordered along the axis of the sarcomere'.  That's not a lot of information, and we know this from other experiments.  But it is information nonetheless because they have some spatial organization.