But many more of those students (including many not in the contest) could solve those problems given more time than the 4.5hr sessions.

If these problems were important to solve, redundantly by thousands or millions of people (like the real work that most people do), far more people would put in the effort to learn how to solve these problems.

It's just a weird comparison. Contests are very artificially structured in ways that don't make sense for comparing to computers.