The weighting of college admissions exams (which are heavily weighted toward measuring ability rather than study skills) and high school grades (which measure a combination of study skills and ability, such that you can't pull the two apart distinctly) in admissions means its easier for someone with high intelligence and weak study skills to get themselves in over their head in the college program they are admitted to than for someone with less intelligence and stronger study skills to do.
Plus, the difference between not having study skills and needing to learn them from scratch and having study skills but needing to study more is one of kind, not merely of degree.
(But, sure, lots of people have transition problems with college, even though those problems can have different sources, natures, and manifestations.)