While I don't doubt that what you say is true, systems which, by spec, should be able to handle a given situation, that then years after they were written finally are called upon to handle that situation, fail more often than not.

The CEO also said they would pay $100million to clean up, which is not chump change, even for them I bet.

I'm not saying they were blameless, but I think most systems which have never had a given variable go negative, that years after they were written finally have that variable go negative, will have problems.