Jack,
I agree it was somewhat inefficient, but as far as I know, this is the only branch that had this. I don't recall seeing any signs of a turntable on this line, but the space where the terminus is located is pretty tight with the multiple passenger tracks and freight house. Both the New Haven/Boston and Albany built one of these loops at Boston's South Station. This may have been used to turn the big passenger consists such as the Senator, New England States Limited, or Lakeshore Limited that came in. There were once big coaching yards now buried under high rise office buildings and a highway located a bit south. All of that is gone but the loop still exists. There was a similar loop at North Station in Boston that once served the Boston and Maine (B&M), and visiting roads.
Here's the South Station loop:
http://binged.it/1iavRYh
The site of the North Station loop.
http://binged.it/1cRVckr
This is now the MBTA CR engine and train terminal. The old loop used to go around the old roundhouse located on this site.
What's odd is I never remember seeing escape tracks that these terminals for the engines to leave. Maybe the process was to pull in engine first, uncouple the engine and turn the train while the engine was sent to the engine facility for maintenance before everything was setup again for outbound service.
Sadly, much of this took place long before I could remember as the long distance trains disappeared before I knew any better from the north side and this became a commuter station.
South Station even had an earlier loop built right under and around the station. This was used to turn commuter trains which stopped on a lower level. When service ended I can't remember, but the loop was long forgotten until some construction was being done down there for the infamous Big Dig and one of the loop tracks was rediscovered. The track was still in place, but can no longer be used because the radius and tunnels are too tight for modern equipment.
http://i203.photobucket.com/albums/aa26/veryunusual/SouthStation1904.jpg
Here's an old picture dating back to when the station first opened. Part of the loop can be seen on the right.
John