Mar 11, 2018 - 10:25 AM
Yes, the Swiss Travel Pass is a better option if your only train trip in Austria is Salzburg to Hallstatt and then on to Chur.
The Glacier Express is covered by the Swiss Travel Pass but not the mandatory reservation.
You can see which routes are covered with the PDF map noted here. Below the map link is a list of major attractions that are either fully or partially covered by the Swiss Travel Pass.