We should take a step back. The location of the recording doesn't matter so much (though sometimes it does matter). The bigger idea here is that some interactions between citizens and LEOs are private matters and not in the public's interest.

As an anecdote, when my friend was the victim of domestic violence, she confided her history with her abuser to an officer, and that officer gave her very individualized care. Whether their conversation happened inside a bedroom, at a front door step, or at a public park doesn't matter. My friend would not want her abuser, her estranged family members, or anyone else to a hold of the conversation she had with the officer.