Use of 'they' if sex is unknown is normal I'd say. This is not the case here it seems though, so a complaint is valid. I do not think a formal 'they' is improp

Use of 'they' if sex is unknown is normal I'd say. This is not the case here it seems though, so a complaint is valid. I do not think a formal 'they' is improper, or a new innovation e.g. see comment here (https://www.lexico.com/en/grammar/he-or-she-versus-they https://www.lexico.com/en/grammar/he-or-she-versus-they) (I might amend this later to add some examples with some google-fu, but it shouldn't be hard to find some 17th-century prose). See also the comments and answers here https://english.stackexchange.com/questions/108457/is-using-she-when-the-gender-is-unknown-ungrammatical. https://english.stackexchange.com/questions/108457/is-using-...) That said, the author misuses and misapplies the construct, as the gender seems known to me from a quick pass of the article, and as mentioned by other commenters. Yes, it feels forced and it usually doesn't -- you probably have already encountered similar examples before, but did not notice them.