That's interesting about that screen. I had never heard about this before. Someone on here had also mentioned that they didn't believe the cars were parked in their usual spots. possibly because another car was parked there. That would mean someone was already there before the girls drove there.
They could have parked differently because it was graduation. Sherrill's car could have been in the garage port if other people stopped by earlier. She might not have wanted anyone including neighbors or friends to pull up to her house. I also wondered if a cop or someone impersonating a cop pulled them over near the house they would go into the circle. Suzie pulling into the circle would make it easier for Stacy to follow her and not block Sherrill in. Also if someone else came to the house saying "you can't stay because you are blocking my mom's car in" might be a way to get someone out. Just random thoughts.