Originally Posted by
mconlonx
By the look of the design, I bet tightening torque is important on the bolts. They force the underside of the seatpost head against the protrusions that are missing, yes? So severe overtightening might put more force on them than spec'd... leading to a break. Not saying the OP did so, just sayin' it looks like a possibility with that particular design.
I would agree with this, but I hope you agree it's a poor design.