They simply apply for the major they want - if majors are required. Some kids seek rank and if they want business and a school doesn’t offer, they choose econ, as an example.
Some will choose data science instead of computer science, if they think it’s easier. Or a different college within a U if they think that college is an easier entry.
Some will be all over - maybe they applied for one major and then changed their mind b4 the next school.
Most ECs, if not all, work for all majors. And a story can easily be told if required.
I believe in major over school. If I want to be an accounting major, I wouldn’t go to a school that didn’t offer it.
At some schools, you don’t declare a major up front.
In sum, every app is independent of another.