OnValidate() not called when stored ScriptableObject is called

I have the following structure:

 public class A : MonoBehaviour
 {
     public Data data;
 
     private void OnValidate()
     {
         // do something with data
     }
 }
 
 public class Data : ScriptableObject
 {
     //some data
 }

Is it expected, that A.OnValidate() isn't called when a value in Data changes?

If yes, is there another way that's more elegant than a System.Action?

The Code is supposed to run in the Editor.

Thank you very much for your help!