案: why is a bench also a case?
Your understanding seems to be correct. For example, in Liu Yuxi of Tang Dynasty's 《陋室铭》:


  无丝竹之乱耳，无案牍之劳形


Where 案 means the desk, and 牍 is a type of hard wood board or pad, on which you write articles. Put together, the bisyllabic word simply means cases, articles, or documents.