Discussion Disable Reload Scene Works Inconsistent

Reload Domain Enabled
Reload Scene Disabled

Unity - Manual: Scene Reloading (unity3d.com)

1. ScriptableObject and MonoBehaviour fields that are not serialized into the build ([NonSerialized], private, or internal) keep their values. This is because Unity does not recreate existing objects and does not call constructors. Additionally, Unity converts null private and internal fields of array/List type to an empty array/List object during Domain Reload and stay non-null for runtime (non-Editor) scripts.

In my opinion there are some unexpected situations.

It is not mentioned in the documentation, but does not keep reference type's values except string / List<bcl types/string>.
Its keeps int or any other bcl type but doesnt keep custom value types.
Its keeps string value but non keep object or custom reference types. I think it might be using a Char[] approach for the string, but I'm not sure.
Its keeps List<string/value types> but non keep List<object/custom types>

I suspect that this is related to Domain Reloading because when Domain Reload is disabled, these values are preserved.

Code (CSharp):

1. public class Test: MonoBehaviour
2. {
3.     private int _int;
4.     private TestStruct _struct;
5.     private object _object;
6.     private string _string;
7.     private TestClass _class;
8.     private List<object> _objectList;
9.     private List<string> _stringList;
10.     private List<TestClass> _classList;
11.  
12.     [ContextMenu("InitializeInEditor")]
13.     private void Initialize()
14.     {
15.         _int = 1;
16.         _struct = new TestStruct { X = 1 };
17.         _object = new object();
18.         _string = "Unity";
19.         _class = new TestClass();
20.         _objectList = new List<object>();
21.         _stringList = new List<string>();
22.         _classList = new List<TestClass>();
23.     }
24.  
25.     private void Awake()
26.     {
27.         Debug.Log($"Int is null: {_int == 0}");
28.         Debug.Log($"Struct is null: {_struct.X == 0}");
29.         Debug.Log($"Object is null: {_object == null}");
30.         Debug.Log($"String is null: {_string == null}");
31.         Debug.Log($"Class is null: {_class == null}");
32.         Debug.Log($"List<Object> is null: {_objectList == null}");
33.         Debug.Log($"List<string> is null: {_stringList == null}");
34.         Debug.Log($"List<class> is null: {_classList == null}");
35.     }
36.  
37.     private struct TestStruct
38.     {
39.         [NonSerialized] public int X;
40.     }
41.  
42.     private class TestClass
43.     {
44.  
45.     }
46. }

Resuts
Int is null: false
Struct is null: True
Object is null: True
String is null: False
Class is null: True

List<Object> is null: True
List<string> is null: False
List<class> is null: True