Why UI event handlers dont get memory leaks if listener not removed

Questions & Answers
1

I’ve seen common practice that users usually just AddListener, but never remove if listening gameObject is being destroyed.

myButton.onClick.AddListener(()=>MyFunk()); }

Is this handled behind the scenes, or Listener removal should be a must in Unity too?
Personally i always remove it, im just really wondering.

OnDestroy()
	myButton.onClick.RemoveListener()...
}
2

I could be misunderstanding the wording of the docs but AddListener is meant to add a non.persistent listener.

But, the following shows a weird behaviour (at least until I get it explained):

private float myFloat = 10f;
[SerializeField] private Button button = null;
void Start( )
{
	button.onClick.AddListener(MyMethod);
	DestroyImmediate(this.gameObject);
}
public void MyMethod()
{
	Debug.Log("Call " + this.myFloat);
	this.myFloat ++;
}

the best part being that the object is surely gone, the this.myFloat still gets printed AND increased, and I don’t have any persistent listener.

If I remove in Destroy then all goes fine. It seems the AddListener is creating a link to the object in memory and even triggering the GC will not collect the object. Using a weak reference would probably bring it back to life I am thinking.

What is even better is that if I create a reference to my script above and call for the myFloat value, I get it!!! Despite the inspector showing Missing(Type)!!!..

This tells me that we have here a memory leak if the programmer is not removing the listener manually, until I am proven wrong. obviously.