While not true in this scenario, there are a few locations that utilize the L notation to show that the train stops primarily to discharge only, and may depart up to five minutes early.
The other nugget in all of this, is that in order to effectively increase the speeds of a train they will need a dedicated fleet of Viewliner II's allocated to them, unless Amtrak goes back to get the Viewliner I's upgraded to 125 mph standards (they are currently rated for 110 MPH). The only train that would be able to get away with interchangeable Viewliner I's and II's is the LSL, since it's restricted to 110 MPH because of the AC-DMs, MNRR, etc. But for the trains where the vast majority of the fleet is used (Silver Service, Crescent, Cardinal) you can't change the timetable without the upgrade to the I's. Sure, if you can get a consist together that will allow you to move at that clip they'll likely open the throttle up and run it at 125.
The benefit that most are forgetting is that an all Amfleet and Viewliner fleet will mean the Engineers will be able to run blended braking on these trains. You're not supposed to (emphasis on the word supposed) run blended braking on a train that has Heritage more than one Heritage in the consist (IIRC). Blended braking means a better ride for the passengers, and a few seconds saved on the station stops, curves, and slow orders.