Re-cuts by their nature are hard to discern because the re-cut can truncate the original cut in part and be completely in the confines of the original fill in other parts. They can even be absent from the record. Cutting is the reason why not all past activity on a site leaves traces of its existence in the sequence.
Re-edits are hard to identify because they can cut portions of the original edit and exist entirely within the original footage at other times. Sometimes, they may even be missing from the record altogether. The reason why we cannot always trace past activity on a site is due to cutting.