I think they ran out of jerseys, but I think they used some old jerseys. It's possible some of the short boats didn't have jerseys. One year a pinned boat closed down the rapid and there was massive upset, and the person who crashed and shut the rapid down was a racer. I can't imagine the SHAME if you pinned/lost your boat in there after a beat down, shut the rapid down, and you weren't even a racer.
Really good boaters lose their boat in that rapid, so my point is shit can happen. It's kind of like walking down the stairs of Tallulah with your gear on, ready to go so as to help the line move faster... Sneaking go left on race day is just the polite thing to do.