The concept of "safety margins" in physical engineering are largely nonsensical in a software context. In physical systems, correctness is a bulk statistical property of the design, an aggregate of probability distributions, which makes safety simple. If you are uncertain, add a bit more steel just in case, it is very cheap insurance. Physical systems are defect tolerant, they aren't even close to defect-free.

In software systems, correctness is binary, so they actually have to be defect-free. Defects don't manifest gradually and gracefully like they often do in physical systems.