As described in SERVER-17148 (and more details in SERVER-80423), the catalog interface for deleting a document always requires a snapshotted BSONObj even for delete-style operations (e.g. findAndModify with remove: true) which can theoretically use a covered index scan without fetching the full document from disk.

From the query-side, we can somewhat trivially remove the fetch however it doesn't help performance much if there isn't a more efficient method for deleting a document (and all index entries associated with it) via recordID alone.