Why not South Station?

Assignment: Pick up my brother's mother-in-law at the bus terminal at South Station. She is arriving at 3:25 PM. Challenge: Find out what bus line she is arriving on and see if they provide an arrival status. Search and find the South Station Transportation Center web site. If you follow the link, you will see that it lists two bus lines (Greyhound and Peter Pan). Neither of these lines have a bus due into South Station at 3:25 PM. So some other bus company must be involved. Any other information on the web site about the full listing of bus lines? No. Nada. Turn to Google again, and search for buses from and low and behold, there it is. So why would South Station not list this or any of the other bus lines (I stopped looking after these 6) on their web site? Concord Trailways Chinatown Bus Lines Fun Wah Bus Lucky Star Plymouth & Brockton Vermont Transit Lines There are at least a few more based upon the logos of the buses in the transportation center. Why not list them all?