I’m pretty sure humans make mistakes too and it happens rather frequently that nobody catches them until it’s too late. In most fields we’re okay with that because perfection is prohibitively expensive.
Obviously systems have always had to be resilient. But the point here is how dangerous a "set it and forget it" AI can be. Because the mistakes it makes, although fewer, are much more dangerous, unpredictable, and inscrutable than the mistakes a human would make.
Which means the people who catch these mistakes have to be operating at a very high level.
This means we need to resist getting lulled into a false sense of security with these systems, and we need to make sure we can still get people to a high level of experience and education.