In jamʿ, the defining feature is a common judgment about several things. In muraʿat al-nazir, the defining feature is congruity among related ideas, whether or not a common predication is expressed.
“Pen, inkpot, paper” may exemplify thematic congruence. “Pen, inkpot, and paper serve learning” additionally places them under one assertion. Both devices can occur together, but they are not identical.