Imagine this situation... you have translated your entire application, some time later you need to change some screens and text labels, and now you need to check which translations need to be updated. Wouldn't a filter by Pending Translation be nice in this situation?
To do that, probably, the platform would need a boolean attribute to mark that translation was updated (or done), for each item in the Edit Translation screen. This attribute is reset by the platform, for example, when a corresponding text label in the application screen is changed.