Except the binomial assumption obviously does not hold because
(a) failures are correlated, not independent, and
(b) many failures happen not at the component level but at the plane where components interact, and regardless of how much redundancy there is at the component level, there is ultimately just one plane at which they finally interact to produce a result.
(a) failures are correlated, not independent, and
(b) many failures happen not at the component level but at the plane where components interact, and regardless of how much redundancy there is at the component level, there is ultimately just one plane at which they finally interact to produce a result.