What it means is, People who learn OCaml generally have to learn something else too. Because the jobs just aren't there. Which in case the person is better off learning that something else properly.
I generally pass over resumes where someone doesn't list at least one programming language that isn't very marketable, fashionable, or part of C's extended family. It's a quick way to winnow out folks for whom programming is likely to be more than just a paycheck.