"Why did a book published in 1969 not contain up to date thoughts of gender and gender terminology from 2026?"
I don't know. It's an absolute mystery to me. After all it's a well-known phenomenon that language never changes, that popular and accepted terminology never changes, and that all text ever written is timeless and static and never drifts in expression or meaning.
Hwæt! We Gardena in geardagum,
þeodcyninga, þrym gefrunon,
hu ða æþelingas ellen fremedon.
Oft Scyld Scefing sceaþena þreatum,
monegum mægþum, meodosetla ofteah,
egsode eorlas. Syððan ærest wearð
feasceaft funden, he þæs frofre gebad,
weox under wolcnum, weorðmyndum þah,
oðþæt him æghwylc þara ymbsittendra
ofer hronrade hyran scolde,
gomban gyldan. Þæt wæs god cyning!
English has never changed even once in its history!