مَا حَضَرَ إِلَّا خَالِدٌ.
No one attended except Khālid.
مَا حَضَرَ خَالِدٌ إِلَّا صَبَاحًا.
Khālid attended only in the morning.
Both use “mā ... illā,” yet the first restricts the attendee, and the second the time of attendance. The first does not tell us when Khālid arrived. The second does not exclude the attendance of others.
Identifying a restriction device is only the first stage of analysis. One must specify what is restricted, to what, and against which alternative the statement is directed. Otherwise an apparently correct label conceals an incorrect reading.