It's one thing to hide the information like the research trees(and that would give an advantage to expirienced players), and the other thing is to hide an information that can be tracked with a pen and a piece of paper. It's just a convenience issue, once you stun an alien you know exactly who it is and how it looked like. I use the list of captures, but it's easier to list the names and use a picture for reference. It's easier than putting sebillians in the list like PURPLE ONE WITH NO PANTS ON