A major function of a qualifier is kashf, uncovering or clarifying an intended meaning. A noun may be understood in outline yet leave a relevant aspect insufficiently explicit.
كَاشِفًا عَنْ مَعْنَاهُ
An attribute that reveals or makes its meaning clear.
“Body” already presents a concept, but “a body extended in length, breadth and depth” foregrounds its dimensional character. The objective is not always to select one member of a set; it can be to unpack a single conception.