Well, I can certainly believe it. The screws that hold the shock in place are relatively small 6 mm. screws. I don't have the torque limits handy for metric fasteners, however, the limit on a 1/4" socket head cap screw is only 14 ft.-lbs. If you exceed this by much, you will definitely snap the fastener.

Just for a comparison, a 3/8" socket head cap screw (slightly less than 10 mm.) is limited to about 42 ft.-lbs.

I cannot tell you why the Haynes manual specifies 33 ft.-lb., but, it is definitely wrong.