------Update:  This issue has been fixed in version 2021.2, 2020.5 and 2019.11.-----------

ElumTools does not have access to linked model Phase Mapping information (due to limitations in the Revit API). Because of this, demolished elements from linked models may be incorrectly included in calculations. Enabling the Filter by View Visibility setting will correctly handle phasing from linked models but may introduce a small performance penalty when initializing calculations (likely only to occur with very large models).

You can also use the calculate by view commands once isolating the geometry of interest in one or more 3D views (Calculate Active View, Calculate Multiple Views).