I think that the plugin adds a post/page to Modified Posts too quickly.
If I edit the URL of a post/page, then I go check it out, and then I notice that there's a typo, so I go back to re-edit the URL, Redirection will record the modified URL and create a redirection for it.
It might make sense to have a minimum age of that URL before automatically recording it. If that's not possible, maybe a minimum age of the post/page, e.g. 5 minutes since publication. During those 5 minutes, a user could be free to change the URL as many times as possible without having a redirection be created.