alt Hacker NewsPeople say that but I think it's gaslighting. I got marked down for using singular "they" in any writing I did in school in the 1980s. I didn't start to see it as a common "gender neutral" pronoun in professional writing (e.g. newspapers) until the last 20 years or so, and really not commonly until the past decade. It still trips me up when I see it used, I have to go back and make sure I didn't miss that more than one person was being discussed.
I suppose one could go back and look at popular style guides from the 1980s and 1990s and see if they endorsed it.
They were teaching us that in the 1980s, yes, but it was an overcorrection. They also taught us not to split our infinitives. That was BS as well. I see no need to maintain standards that were originally imposed by grammarians who undervalued English and overvalued Latin. These days we would call that linguistic insecurity.