Bizarre. I think he's right about the torque going through the outer edge of the shafts, (many years ago on here was a discussion about drilling out the centre of half shafts for this reason plus reducing the stress)
If the joint faces are perfectly square and done up really tight, the friction between them ensures that the force transfered to the outer region.
Even so, it does not seem right, especially with the grub screws, they should have been staggered as opposed to being I the e same plane.