An element of your argument relies on defining a liberal arts education in a specific way that is by no means the accurate or sole definition. American schools are quite unique in that, as opposed to universities in the UK, there is something called a "liberal arts education," which in that context is taken to mean the concept of a core curriculum / general education requirements. There is no reason that a liberal arts education as you define it is inherently interdisciplinary, there is no reason that whatever advantages you claim stem from interdisciplinary studied is not covered under a core curriculum definition of liberal arts.
Nelson seems to think they don't.
You're seriously misinterpreting what he says about how modern degrees don't impart critical thinking skills. His criticism is directed at Ivy League educations in general - not only pre-professional degrees but also liberal arts degrees: "I didn't have habits of mind that a liberal arts education was supposed to have given me. And not only did I not have it, none of my other colleagues had it—people who had graduated from Princeton and Harvard and Yale." It bears noting that Harvard has no pre-professional degrees except engineering (no business degree); it's clear his criticism is drawn out of his disappointment that a liberal arts education was supposed to give him and his colleagues critical thinking skills, but failed to do so.
Furthermore, the instant I looked at the link you posted, I could already tell that that wasn't actually the degree requirements for Wharton (I could tell that those were the requirements for a major but not for graduation). So that's a really poor example. The full degree and graduation requirements are listed here: https://spike.wharton.upenn.edu/ugrprogram/advising/curricul...