I'm pretty sure it's just inexperienced workers with zero training or experienced supervision making obvious, predictable mistakes in food preparation (over-baking, failing to evenly apply icing to pop-tarts, etc).
Your reading seems like a very big stretch given how pedestrian most of these mistakes are.
You don't have to work to put insect larvae in food, especially grains. It's separating out larvae that's the usual challenge. Seems like exactly the kind of QA challenge you'd have with a completely green workforce.
I'd assume these production lines involve contact with any number of plastic parts that could break or shave off if operated incorrectly. Same with the glue from packaging hitting the food if you don't do it right.
eg) https://twitter.com/RespectableLaw/status/147225737151065293...