Another tiny fix to #32911

src/EFCore.Relational/Query/SqlExpressions/SelectExpression.cs

@@ -2128,7 +2128,7 @@ public void ApplyUnion(SelectExpression source2, bool distinct)
                         // If the top-level projection - not the current nested one - is a complex type and not an entity type, then add
                         // all its columns to the "otherExpressions" list (i.e. columns not part of a an entity primary key). This is
                         // the same as with a non-structural type projection.
-                        else if (type is IComplexType)
+                        else if (projection1.StructuralType is IComplexType)
                         {
                             var outerTypeMapping = column1.TypeMapping ?? column1.TypeMapping;
                             if (outerTypeMapping == null)