Is "recorded history" redundant?

One of definitions of history is:

The whole series of past events connected with a particular person or thing.
‘the history of the Empire’

Clearly, some of these events can be recorded, and some not. If there was no one recording these events at the time they took place, and we have learned about them through other means, they are still history - but they are not recorded history. Consider for example the history of the Moon (to take an extreme example).

Logic apart, the phrase never in recorded history is a figure of speech, similar to since time immemorial or for as long as I can remember and such. I don't think any of these are meant to be taken literally.

It's worth noting that the idiom since time immemorial is defined by the McGraw-Hill Dictionary of American Idioms and Phrasal Verbs as:

since a very long time ago. (Literally, since time before recorded history.)

(emphasis added by me)

Go argue with that.

It really depends on how you define "history." If your definition states that to be history someone must have preserved the information, then yes, it is redundant. But one could also look at history as anything that has ever happened. Of those events that have happened, only a small percentage of them are witnessed, remembered, and eventually recorded. Also, it depends on what you mean by recorded. Do oral or pictoral methods count, or must it be written? If other methods don't count, why not? What makes them different?