Thanks for posting this, Terry. I had no idea such a study had ever been conducted.
I can verify what you said about being counseled ordered not to reveal what you had been instructed about accepting alternative service. You couldn't agree ahead of time on anything. It was considered "making a deal" with the military. You were only allowed to comply with whatever sentence you got. I know this for a fact. My dad was a long-time "servant," now called "elder," and I heard him telling the same thing to my draft-age cousin who was facing the same thing you did. He went to prison, too, but I'm not sure exactly how long he was in.
About the same time, another young JW I knew was actually sentenced to do hospital work. When his term was up, the hospital immediately hired him and he had a long and successful career with them. Talk about unequal treatment and outcomes.