The two assembly members being compared have different category

Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0)
Since: 2012

Syntax

C#
`public class AssemblyMemberDifferentCategory : AssemblyMemberDifference`

Visual Basic
`Public Class AssemblyMemberDifferentCategory _ Inherits AssemblyMemberDifference`

Visual C++
`public ref class AssemblyMemberDifferentCategory : public AssemblyMemberDifference`

Inheritance Hierarchy

System Object
Autodesk.Revit.DB AssemblyMemberDifference
Autodesk.Revit.DB AssemblyMemberDifferentCategory