I worked my way up to production engineer from apprentice floor monkey at a fab shop, When we got crap steel from a supplier, we didn't buy from them again. I'm familiar with QC too but not the iso 9000 specs.
You don't cast or forge just one or two bad hooks by such a large margin in a batch. Note that the hook didn't snap but rather deformed enough to be described as straightened.
It's easily explained as exaggerated claims to make sales but then when does that ever happen?