Remember, they will have an in-depth look at your financial from the CSS profile, which UNC will use to determine how to distribute their institutional aid. They feel that they will not need it in subsequent years because they expect this to remain relatively stable. If there is a major change in finances, trust and believe that the family will contact UNC-CH and will provide all of the supporting documentation.
As you see, they require the FAFSA to make sure that students remain eligible for aid. They will give the student any federal aid that the student is eligible for (including federal loans) based on the FAFSA. It does not mean that they will meet your FAFSA EFC.