No, there isn’t any point in that.
All docs relating to metaboxes are probably inspired from the wrong code at the codex which use a nonce.
The problem which nonces in metabox inadvertently solve is avoiding data corruption when the quick edit feature of the posts list page is used (or thinking about it any sort of external API as well), as at that point there is no metabox and no data in the form. This can be tricky especially if you have checkboxes in the meta box, but the better way to solve it is by having an explicit hidden input that will indicate that the metabox was displayed (basically this is what the nonce does but it is confusing as it has nothing to do with security).
As for sanitation and validation, you should always do it, because users can send bad values to your code which might even be a legal input. It helps with security but it is not the only reason you should do it – https://xkcd.com/327/