I don't think he means they're structurally weaker, but when they're built, it's with the intention of being ran on perfectly smooth tracks and not speed bumps, pot holes, etc.. It seems to me that a lot of racing accidents involving this type of wheel does tend to break it, usually the barrel away from the center.
Farkas, reading that you don't expect this to be the last time, makes me cringe at the thought of that car getting the fenders or quarters damaged if it does happen again.