Those don't seem like mutually exclusive statements to me. In fact, they feel like two sides of the same coin. It's almost by definition that more advanced control systems are exactly the ones where tractable sources of error (mechanical, environmental, etc) have been eliminated, controlled or otherwise accounted for as much as possible, to the point that the only remaining likely problems come from where the system interfaces with humans in some way.

Which makes those interfaces the most critical parts of the system.