This statement assumes the people you meet in college will be a random cross-section of the entire undergraduate student body. But it really doesn’t work like that at a large university. If you’re a student in Ross, Michigan’s business school, you’ll mostly take classes with and are much more likely to socialize with other Ross students, who as a group have academic stats almost indistinguishable from those at Penn’s Wharton School. Engineering students will naturally spend more time with other engineering students, who as a group have academic stats well above those of Michigan’s other undergraduate schools (except Ross). I got my undergrad degree at Michigan ages ago, but as a freshman I opted for the honors program (open to roughly the top 10% of the entering class), lived in honors housing, and took almost entirely honors courses my freshman year. As a sophomore I accelerated into upper-level courses, mostly with juniors and seniors, and by my third and fourth years I was taking mostly graduate-level courses where my peers were grad students in one of the most highly respected and truly elite graduate programs in my field (philosophy). And that’s certainly not unique to my major. Math whizzes take accelerated classes with other math whizzes, including elite mathematics grad students. And so on.
I don’t mean to suggest these academic units are completely walled off from each other; there’s lots of mixing in student organizations, ECs, at parties, etc. But your social circle will be far from a random cross-section of the class, and if you’re a top student in a rigorous program you’ll tend to have far more interactions with other top students than with others.