Suppose the factual event is that Khalid submitted a document. Three purposes may call for three different formulations:
قَدَّمَ خَالِدٌ الْمِلَفَّ.
Khalid submitted the file.
إِنَّ خَالِدًا قَدَّمَ الْمِلَفَّ.
Khalid did indeed submit the file.
مَا قَدَّمَ الْمِلَفَّ إِلَّا خَالِدٌ.
No one except Khalid submitted the file.
The first can supply neutral information; the second may address doubt about submission; the third can identify or restrict the submitter. If the dispute concerns which file was submitted, the third expression restricts the wrong constituent despite being grammatically well formed.