You are right, also i see two things in the implementation of this factory.
 
1.- Implement the method of the detection if have to mockup the api, using a factory. (In this case the query string). 
2.- The notification that the api is mocked, by a property in the mockSwitch factory instead the HttpInterceptor object. 

However, for the notification i'll prefer using events. 

Also,  an idea it's possible, do the separation as following:
- Add a parameter in the options object of $http service:
```javascript
$http({
  method: 'GET',
  url: 'http:/server/people',
  apiMock: true // 
})
```
This also, give the ability to mock a specific requests.

If you want do it for al, only need to configure the option in the config phase or run method of the application.