In simple terms, this is a duty for organisations to be honest and open with people in their care when things go wrong.
When mistakes are made, especially the more serious ones, fear of consequences drives the natural urge to hide things and cover up, to avoid bad consequences. With staff, this is often the fear of losing their job and reputation among fellow staff, and for organisations it may be the fear of bad publicity, loss of contracts, and regulatory action.
To err is human, everyone makes mistakes. A culture of openness and a blame free culture becomes a learning opportunity and makes staff more confident in admitting mistakes and working to improve systems and processes.