FOI is a law mandating these public records be provided on request -- with various exemptions and allowances for redacting information that could be reasonably seen as a violation of privacy. It's not about being "somehow better", because legislators have deemed that bureaucrats cannot be trusted to decide whether transparency is a good thing.

Consider the example you brought up -- it is against the law for a state employee to send a friend that kind of information, and I imagine that that law exists because politicians feared that kind of murderer scenario. How exactly does that murderer use a cache of email metadata and redacted messages to go after his victim?