I'm not going to write the wall of text that's required to properly describe the situation but that's just not how these systems work. Industrial automation has all sorts of feedback loops so they people operating it know if they can trust it. The people using it are pretty much always trained in how to run the various systems manually so that an errant sensor doesn't turn into a clogged up rail line or waste whatever is in your process equipment that happens to be mid-cycle.

This isn't some consumer appliance where you have to stupid proof every inch of it. These systems are bespoke and their architecture is mostly a matter of business decisions and not at all a matter of the internet peanut gallery trying to figure out how safe they can make it.