Older generation ICs
At one time, I also made my living engineering safety-critical systems.
Selection of last generation or older components for newer applications (like 186s for 777s) is effectively required to certify some systems. It's one of those small win-wins - it's typically a lower-cost component, but its maturity provides reliable failure rate figures and any (ahem) weaknesses in the component are known and can be engineered-around. It can be a feature, not a bug.
Regards redundant software written by different teams, I participated in one such effort that used diverse hardware and software. It's an immensely expensive proposition, with little practical advantage (Leveson's et al fine work notwithstanding).
A little thread drift, but I'll go no further.
Fascinating threads on this subject - I'm learning much.