The advancement tokens are used for creating good combo cards. These are theoretically finite in that once you have maxed every Dan you can no longer obtain them without resetting your skills and I don't even know if that would work. This means that having this being an aspect of the advancement tests will give you an opportunity to obtain more seals than if you were simply to progress from Dan 1 > Dan 3 on every skill. It's basically required so that you can have a non-finite supply of a consumable material.