The study concludes that those who work with a coach do better than those who don't. This is not surprising but it is important.
http://startingstrength.com/article/wndtp
Did you read the study? That's not at all what it concludes. The major conclusion: "Even in the self-selected Starting Strength community, most of those trainees failed to follow The Program." Not explicitly stated in the conclusion section, probably because, as they noted, they had to pare down the data so much, trainees ego follow the program more closely do better at achieving the program's goals.
Collecting data from coached trainees is part of their "next steps"