In general, in aviation, the existence of any single point of failure (SPOF) is considered a systemic issue, be it a single human who can fail (anyone can faint or have a heart attack), a single component, or a single process. That's why there are not only redundant systems, but redundant humans and even redundant processes for the same task (you can power the control surfaces hydraulics through the engines, then through the aux power unit, then through the windmill... ).

If a design contains an SPOF, then it's a bad design and should not be approved until the SPOF is removed by adequate redundancy or other means.