From the intro of Le Guin’s Language of the Night, 1989:
The principal revision involves the so-called “generic pronoun” he. It has been changed, following context, euphony or whim, to they,
she, one, I, you orwe. This is, of course, a political change (just as the substitution of he for they as the “correct” written form of the singular generic pronoun—see the OED--—-was a political act).
She was way ahead of bringing back the singular “they”, which was
around as early as 1375:
In the eighteenth century, grammarians began warning that singular they was an error because a plural pronoun can’t take a singular antecedent. They clearly forgot that singular you was a plural pronoun that had become singular as well. You functioned as a polite singular for centuries, but in the seventeenth century singular you replaced thou, thee, and thy, except for some dialect use.