As promised, I asked two sections’ worth of undergraduate students (about 40) about “the Southside of campus.” What I decided to do was present the sentence to them in its original context — that is, I gave them a copy of the article. I asked them to read the first couple sentences and report anything they found grammatically unusual or even straight-up wrong. Now, it is a newspaper article so there are already all sorts of things you don’t see in other written genres. But in any case, there were a few people who had identified the Southside bit as a little strange, though not necessarily why.
Then, I wrote the phrase up on the chalkboard and immediately many more people saw the strangeness that I had. And when we got into a discussion of the phonology and syntax of compounds, I think everyone became convinced that there was some shoddy writing or editing going on.
I would say that there are many many syntactic or semantic phenomena that are of this nature: presented in isolation, what is interesting about them is immediately apparent, but presented in a natural context, even with instructions to seek out anomalies, they may as well be invisible. I guess part of the job of (a certain stripe) of syntactician is to be hypersensitive about such things; and part of the job of an instructor of syntax is to teach by example.