This is also how the UC system works: the top 9% (IIRC) students are eligible for guaranteed admission, but they are not necessarily admitted to the campus or program of their choice, so you might not get to go to eg Berkeley.
Do they take into account what you intend to major in? Not all UC campuses offer all degrees. If you are in that 9% and want to major in, say, mathematics, will they try to make sure that you get into one of the campuses that offers that?
Why are there any majors that are only offered at a single school? That seems like a much bigger problem than people being able to pick which school they want to go to.
You could have a college major in any possible area of academic inquiry, which means the number of potential college majors is unlimited. Each school can only have so many faculty and they have to balance various factors when deciding who to hire. More resources dedicated to offering new majors might mean less resources going to popular majors that are overenrolled.
