Something doesn't seem exactly right here.
First, where did the shavings come from? That sounds a bit serious. Clearly they weren't left on at the time of manufacture, but they came from someplace.
Second, and this answer may be simple, why couldn't the wrench they were using brush aside shavings? Could be all it could do is come down on top of the bolt.
I'm sure there are logical explanations, but if it were me, I'd be concerned about those shavings.