Why is that strange? Cyanide seems like an obvious thing to test for at scale. Safety engineering doesn't say 'that doesn't seem likely even though it's dangerous and easy to control for so I'll not handle the scenario'. It says, 'anything unsafe should be mitigated with the right cost-benefit analysis applied for the scenario'. Testing for cyanide makes sense regardless of whether it's in the factory.
I really don’t know, but could there be 100 other substances as dangerous and easy to mix/administer as cyanide? There must be some cut off since you can’t test for everything. I’d be interested to know what that test matrix/decision document looks like.
Cyanide is found as an impurity from both natural sources and as a byproduct during the manufacturing process, a lot like lead. So it's common enough to warrant the expense of testing
