change:attribute on unchanged attribute [philosophic]

``` javascript
var m = new Backbone.Model({mod: 7});

m.on("change:mod", function(model, mod){
      console.log("mod changed from " + m.previous("mod") + " to " + mod);
 });

m.set("mod", 8, {silent:true});
m.set("mod", 7);
// mod changed from 7 to 7
```

Is this an expected behaviour?
Wouldn 't be better if no event was triggered for unchanged resulting attributes?
