In 1960 I think BoI reports were 'Secret' and not released to the public for thirty years. Perhaps snippets were published in newspapers - I don't know.The Valiant Spanhoe crash (XD864) warranted only four column inches of basic information in next day's Telegraph - I don't know which page - and less in The Times.
Today we expect all the information to be available to us.
For these reasons, I can't help thinking that the older reports are more likely to be free of outside interference because they were in house - only those that need to know would see them. Today I would have thought the writers of these reports have to keep one eye on public opinion/political implications etc..
I also get the impression that earlier we were acceptiong of blame being placed on the foot soldiers (pilots, train drivers etc.) whereas today we are more likely to look at them as victims of a weak system and put blame on leaders, directors and so on.