That was the case in my mission experience too! I wonder why we haven't picked up on this. When I served, I had friends serving elsewhere in Europe where obedience = baptism was drummed into their heads. They all felt so guilty and depressed all the time. They weren't having success because Europe can be very tough, many aren't that religious, and a lot of people aren't open to strangers coming in to talk about Jesus.the most successful missionaries on my misson were the ones who fooled around and had long hair, knew how to party it up, etc.
We were the highest baptising mission in Europe, and my friends would say "Wow, your mission must be really righteous and obedient." I kept having to assure them that was not the case at all. We had missionaries swimming in the ocean, drinking, missionaries with girlfriends, and so on. We had a lot of autonomy. One time one of my ZLs got on an elevator with my comp & me and said "Ya know, I always wanted to do it with a black girl." I asked if he realized he said that out loud. He was just absentmindedly thinking out loud he said. In short, obedience to the commandments pre-mission and in some cases during the mission was not the secret formula at all. Personally, I think it's because if you have a dodgy past, you're going to relate more to a variety of people, you still chose to do the mission, so you've got good reasons to be there, and you probably have gained a little humility here and there, not to mention life experience.
Personally I think raising the bar was a big mistake. I think instead they should raise the age again (for the men) and give the MPs blinders so they won't be hyper-vigilant about obedience.