From time to time you will see a story about some school that soars in the USNWR rating by tailoring their stats. Don't know if either NU or UF have played that game. I do know that in the case of UF the university and the state made a commitment to make it as 'elite' as they can. With FSU, South Florida and Central Florida among others as in state backups they have been going all out to channel more of the better applicants to UF. With the high school graduate numbers there continuing to rise they have been successful.
Every school does this to some extent, even the Ivies. These rankings while popular are little more than a aggregation of stats that have little to do with the slicing and dicing the quality of education to the extent you can have a definitive ranking.
A better way to look at it is how does a particular school fare in areas that are important to me.
The big number here is acceptance rate. Aot more people are applying to big public schools in warm weather states than they are in northeastern ones.
I also think these rankings are more important to top students that those in the middle, where such nuances won't make much of a difference. The top 1% at FSU will show just fine against the top 1% of most other schools. But if I'm looking at the bottom 30% percentile, they better be from a better school.
The old joke about what they call the guy who graduated last in med school, applies here.