I had the same thought while reading this. The test has a limited range of values, you can only estimate your score within that range, no higher or lower. Those

I had the same thought while reading this. The test has a limited range of values, you can only estimate your score within that range, no higher or lower. Those at the top and bottom will naturally estimate into the body of the range since a lower or higher estimate is not possible. However, I’m not sure this explains the results entirely, and I’d like to see a statistician take this further.