Especially in Germany, albeit with an outsider's perspective, I would say it's very clear how relevant it is how you speak of persons. There is no commonly accepted 'singular they' and e.g. 'teacher' is always male (you'd have to say 'teacheress' or 'teacherin', not sure how to translate it, and so what people do is say both every time they refer to any teacher/in).
When always having to gender every word, not being inclusive has a measurable effect. There are enough studies that show the effects of listing genders alongside job listings that are typical/historical male or female jobs, also in other languages with less gendering. English is a lot better as a language, in my opinion, but still if you say "he" when referring to the aforementioned "doctor" when, really, it could be a doctor of either gender using the patient portal, you are still reinforcing a bias.
I don't think it's unnecessary to include the other half of the population in general writing, even if nobody has studied the effect of a "man in the middle" specifically. There's enough evidence elsewhere so that we might as well just switch things over at hardly any cost of change and no cost at all afterwards.
