Everyone does make mistakes. To Err is Human (Institute of Medicine) was widely publicized research about medical mistakes in hospitals. Read it you'll be shocked. Yes, everyone makes mistakes, but not everyone's mistakes kill people and very often the death could have been avoided. The key with living donors is this is elective surgery. There was 0% chance of death or complication to this patient because they didn't need surgery. Not sure why you think it is really well known that doctors rarely make significant mistakes. The mistakes may be unintentional and caused by human error but does not make them any less significant. In 2008 a surgeon at Downstate Medical Center used a clip on a living donor named Michael King. He bled to death. This clip was recalled and not supposed to be used. The surgeon should have known that (maybe he did who knows?), but he made a mistake. Everyone makes mistakes but this was fatal and avoidable which makes it so tragic. What is the likelihood of a mistake like that? The doctors all quote the infamous 3 in 10,000 deaths. Is it accurate and up to date? i have no idea. But if it happened to me or my family member it wouldn't be .03% dead it would be 100% dead. So statistics and safety really do matter, at least to me.
I think the point about keeping lines of communication open is to avoid making more mistakes. Owning up to them helps to improve quality assurance and make sure another mistake is avoided.