OpenSSL is, I think, another "case in point" example: Heartbleed was an amazingly awful 0-Day that afflicted OpenSSL and I can only imagine how much worse thing

OpenSSL is, I think, another "case in point" example: Heartbleed was an amazingly awful 0-Day that afflicted OpenSSL and I can only imagine how much worse things might have been if Windows didn't use SChannel and FreeBSD (and thus iOS/macOS) didn't use LibreSSL (and if LibreSSL's fork auditing hadn't made a difference in that situation). Even (especially?) highly scrutinized libraries seem to need diversity in implementation to avoid single point of failure problems.