At this point why not just let grads choose any Z (that needs and can handle them).
Someone from the Chicagoland/NW Indiana/Southern WI can get ZAU with the 5/15 and 5/24 lists. They cannot get ZAU with the 5/21 and the 5/31 class. So they'll block an AG from going to ZLC or ZFW or whatever because they have a good shot of eventually getting outta those facilities. While the new system saves people from going to black holes like ZOA (which got 3 volunteers in May fwiw), it's still a very suboptimal matching system.