Take for example the use of "they" to mean he or she. My hunch is that this is at least partly due to recent changes in pronoun use that are meant to avoid discrimination against trans and non-gendered folks."

Surprising that a prof who is so scathing about his students writing style could be so uninformed concerning literature. The third person plural used in the case of an nonspecific individual has a long tradition among many accomplished writers, including Shakespeare and Jane Austin. Indeed this usage was once relatively common, then lapsed, and has recently been revived and accepted by various style books and dictionaries. I have been using this form, unrelated to non-gendered issues, for decades' simply because it makes for smoother word flow than the awkward "he or she." Apparently, Shakespeare and Jane Austin thought so too.