Things may have changed, but I don't recall any group exams during my time at Caltech, and conversely I do recall a strong sense of pride in the Honor Code. Also, if your professor allows collaboration, then it's definitionally not cheating: There is a vast moral difference between "the professor made the assignments difficult with the specific expectation that people will collaborate" and "the professor doesn't want collaboration but people did it anyway".

Frankly, this comment feels almost entirely foreign to my experience—I suppose things could've changed over the years (although my impression is that things have gotten much worse recently, not better), or it could be major-specific, or I just got lucky with the specific people I happened to hang out with?