I don't understand the reason for the passes either. I realize they don't want large groups going into the SRL and then expecting to sit together, but it's the responsibility of the guests to pay attention to the signs. If you can't figure out that "single rider line" means your group will be split up, then you should have to live with not being able to ride with other members of your group.
My sister and I went through the SRL together twice on the 2nd, and nobody said anything. We both ended up on the same train both times, but we weren't even expecting that.