I have seen “one of the only” used correctly exactly once. All other uses of it have been nothing other than evidence of stupidity. Yes, stupidity.
only: without others or anything further; alone; solely; exclusively
Now, admittedly, IF “one of the only” is followed by or includes a qualifier AND eliminates the article “the” (which ALSO signifies singularity, unless a group is clearly designated) bi>like “one of only five,” then the stupid phrase is transmogrified into something that has some sense to it. Apparently, pre-Internet publishers agree with me:
Yeh: the Internet. *sigh* Enstupiating the world by empowering Ortega’s “mass-man.”