This paper gives an Abstract Categorial Grammar (ACG) account of (Kallmeyer and Kuhlmann, 2012)'s process of transformation of the derivation trees of Tree Adjoining Grammar (TAG) into dependency trees. We make explicit how the requirement of keeping a direct interpretation of dependency trees into strings results into lexical ambiguity. Since the ACG framework has already been used to provide a logical semantics from TAG derivation trees, we have a unified picture where derivation trees and dependency trees are related but independent equivalent ways to account for the same surface--meaning relation.