Clarify explanation of property initialization.

The previous text implied (at least to me) that there was something
special in Godot called an "init assignment value", and that there was
special logic determining which kind of assignment was used.  In
reality, nothing special is happening: the property is initialized, then
the constructor may set the value, then exports may as well.

I also harmonized the Godot and C# code samples, rather than expecting
the user to read both in order.

Frankly I almost feel like this would be clearer if the entire section
were simply deleted, but I wasn't sure if that would be accepted.

tutorials/best_practices/godot_notifications.rst

@@ -164,28 +164,39 @@ _init vs. initialization vs. export
 -----------------------------------
 
 If the script initializes its own node subtree, without a scene,
-that code should execute here. Other property or SceneTree-independent
-initializations should also run here. This triggers before ``_ready()`` or
-``_enter_tree()``, but after a script creates and initializes its properties.
+that code should execute in ``_init()``. Other property or SceneTree-independent
+initializations should also run here.
 
-Scripts have three types of property assignments that can occur during
-instantiation:
+.. note::
+  The C# equivalent to GDScript's ``_init()`` method is the constructor.
+
+``_init()`` triggers before ``_enter_tree()`` or ``_ready()``, but after a script
+creates and initializes its properties. When instantiating a scene, property
+values will set up according to the following sequence:
+
+1. **Initial value assignment:** the property is assigned its initialization value,
+   or its default value if one is not specified. If a setter exists, it is not used.
+
+2. **``_init()`` assignment:** the property's value is replaced by any assignments
+   made in ``_init()``, triggering the setter.
+
+3. **Exported value assignment:** an exported property's value is again replaced by
+   any value set in the Inspector, triggering the setter.
 
 .. tabs::
   .. code-tab:: gdscript GDScript
 
-    # "one" is an "initialized value". These DO NOT trigger the setter.
-    # If someone set the value as "two" from the Inspector, this would be an
-    # "exported value". These DO trigger the setter.
+    # test is initialized to "one", without triggering the setter.
     @export var test: String = "one":
         set(value):
-            test = value
-            print("Setting: ", test)
+            test = value + "!"
 
     func _init():
-        # "three" is an "init assignment value".
-        # Trigger the setter
-        test = "three"
+        # Triggers the setter, changing test's value from "one" to "two!".
+        test = "two"
+
+    # If someone sets test to "three" from the Inspector, it would trigger
+    # the setter, changing test's value from "two!" to "three!".
 
   .. code-tab:: csharp
 
@@ -195,37 +206,24 @@ instantiation:
     {
         private string _test = "one";
 
-        // Changing the value from the inspector does trigger the setter in C#.
         [Export]
         public string Test
         {
             get { return _test; }
-            set
-            {
-                _test = value;
-                GD.Print($"Setting: {_test}");
-            }
+            set { _test = $"{value}!"; }
         }
 
         public MyNode()
         {
-            // Triggers the setter as well
-            Test = "three";
+            // Triggers the setter, changing _test's value from "one" to "two!".
+            Test = "two";
         }
+
+        // If someone sets Test to "three" in the Inspector, it would trigger
+        // the setter, changing _test's value from "two!" to "three!".
     }
 
-When instantiating a scene, property values will set up according to the
-following sequence:
-
-1. **Initial value assignment:** instantiation will assign either the
-   initialization value or the init assignment value. Init assignments take
-   priority over initialization values.
-
-2. **Exported value assignment:** If instancing from a scene rather than
-   a script, Godot will assign the exported value to replace the initial
-   value defined in the script.
-
-As a result, instantiating a script versus a scene will affect both the
+As a result, instantiating a script versus a scene may affect both the
 initialization *and* the number of times the engine calls the setter.
 
 _ready vs. _enter_tree vs. NOTIFICATION_PARENTED