I think that in part the desire to use the feminine pronoun as the default neutral is an attempt to prove this effect to male readers -- and to be honest, I do sort of see it myself, despite being a thorough skeptic of the Sapir-Whorf hypothesis of which this is an offshoot.
every time I tried to read the book, I kept tripping up on the fact the protagonist/narrator identifies every other character encountered as "she" or "her" in ways that I knew would not always be accurate, and so I got stuck every time trying to figure out if this character actually was female or not.
I think there is definitely some effect from language onto culture and viewpoint. I think it's more a question of how strong that effect is. Some people certainly overestimate it, but I think it is there. Certainly in English, many people feel an overwhelming need to know whether someone is male or female, to the point of being confused as to how to think about a person or character without knowing. I find it bizarre. It's particularly strong with babies, where people will get angry and be unable to interact with the child without knowing. My impression from people who speak gender-neutral languages (like Finnish, Korean, and Chinese) is that this is less of an issue. So, for example, you could have a minor character in a book whose gender isn't specified, and it isn't considered a problem.
That said, there's still plenty of sexism in those cultures. So I don't think the effect is strong, but I'll buy that there is an effect.
What do they do in other languages where nouns have a gender?
Tell us to remove the vowels at the end of them and replace them with an X, then pretend that it's still a real, pronounceable word and that it helps address real discrimination, somehow.
The "x" ending isn't used in most of the Spanish-speaking world. There is an "e" ending has slightly more adoption, from what I hear, but it's still rare.
(ref) Still, "he or she" is relatively common in Spanish, along with collective nouns instead of masculine default ("la plantilla de la empresa" instead of "los trabajadores").
In Swedish, a new gender-neutral pronoun has been widely adopted, now included in the dictionary but not in formal style guides. As an alternative to "hon" and "han" (he and she), there is now gender-neutral "hen".