Yeah the logic probably being something along the lines of, if you notice that mostly one type of mage makes it to Day 2 you could alter your book to better meet that particular challenge.
Of course, though, everyone else would have that same option, so if you tweak your book based on the popularity of mage X, you might show up the next day and find them all playing mage Y instead.
I know in other games I've played that allow separate lists for different days, some players will deliberately bring their
second best build to day 1 so that they don't tip their hand about their build for the finals.
I don't really have a preference either way, I just wanted to make sure I knew which method was being used.
