They're worth mentioning in articles about those exact type of signings. If Cameron highlighted Morrow as a bargain last year, would he have been right or not?
In fact, I would argue they are not all that rare. Every year, MLBTR runs articles about the best minor league deals. And every year they have multiple candidates.
It looks like Cameron is basically saying players like Fister and Hunter are going to outperform their perceived value, and he offers support as to why. That you perceive them to be insignificant dumpster dives offers more to support his argument than to discredit it.
I actually wouldn't mind Hunter coming to Boston. Not so sure about Fister. When it comes to potential bargain FA SP, I actually like Miles Mikolas more than Fister...