They has been used as a gender nonspecific pronoun for hundreds of years. The author writes "But I see absolutely no reason other than laziness to start subbing our hes and shes with a clunky they, or our hises and hers with theirs"
But she has it backwards. They is being subbed out with a clunky 'he or she' (really, which one is more elegant when you say/read them?). It just seems to me like she is annoyed by the convention and came up with a bunch of reasons why we should agree with her, and simply chose to ignore the facts about its historical usage.