Use of gendered language is marginalizing to nonbinary people.
It's easy to figure out why these changes are being made in particular, once you take a position of empathy.
References to brothers or sisters, or mothers or fathers, is offensive to nonbinary people? In all seriousness, not trying to start a flame war, why is that? Is a reference to hair offensive to a bald person?
The reason to replace an aggregate ‘brothers and sisters’ with ‘siblings’, ‘mothers and fathers’ with ‘parents’, or ‘boys and girls’ with ‘children’ is because for all of these the replacement suffices without calling attention to gender when it’s not necessary to do so.
There’s also an argument that the ‘X and Y’ phrasing makes the ‘X’ seem more important than the ‘Y’, or makes it seem like the ‘default’ - just a little, but with repetition the impression is reinforced. If there’s an alternative collective word to use, it avoids this ‘ordering’ issue with no real downside.
Note that all these arguments make sense in even if you consider gender to be a binary thing.
I do now attempt to use the single-word non-gendered collective nouns in speech myself for the reasons I gave, and I think it’s a good idea to do so.
To discuss the edits to Dahl’s work: I would argue that for these ‘Xs and Ys’ examples he was probably just using the popular idioms of the time rather than choosing them to convey a specific meaning as you say. That would certainly be what I would’ve done, without much consideration, 20 years ago!
But that’s obviously not the case for all the edits that are reportedly being made.
The edits in aggregate do make me uneasy. I’m not sure how I’d feel if they were more limited.
I hate to be the guy that cries “1984,” but do we really have to completely neuter our language to avoid every imagined offense? Are there people out there who’s egos are so fragile that they can’t handle “gentlemen” coming after “ladies?”