> If you're gonna spend 3-6 years of your life there it's worth putting in the legwork

There are over 500 public universities/colleges. Your advice is great after you've made a shortlist. My advice is on making the shortlist to begin with.

> and on the percentage of classes under 20 - that's the exact metric I'm talking about being easy to game.

Technically true, and overly pedantic. I'd put money that 90% of the schools that have that metric actually will have fewer students in the classes in the major of your interest (likely engineering). In the real world, these kinds of counterexamples you speak of are, well, the exception.

Engineering is demanding, and many students drop out after the sophomore year. At least in my department, they had a very clear and open goal: If you don't do well enough in the introductory courses, you will simply be disallowed from taking junior level courses. You needed a B on a key (not easy) course, and a grade of at least 75% on that course's final exam.

I sincerely doubt there are many (if any) universities trying to game that metric. Letting professors teach small classes is expensive. Which is why I said that if a university really has a weird distribution where there are lots of courses with a tiny number of students - that in itself is a good omen!