[EditorButtonAttribute] Method call not work in nested class.

class RootClass : ScriptableObject
{
    public NestedClass childObj;
}

[Serializable]
class NestedClass
{
    [EditorButton(nameof(CallMyMethod))]
    public string testField;
    
    // Method here in nested class wont be called, but in the parent ScriptableObject will work.
    private void CallMyMethod()
    {
         // Will not be called, but expected!
    }
}