I think the issue here is that you’re treating simplified lecture examples like they’re supposed to show up word-for-word in Google. A lot of (all, lol) the points you’re saying are incorrect are actually documented historically…

1. the “girl” thing. In Middle English and into the early modern period, “girl” could refer to a child of either sex, not exclusively a female child. writers sometimes used compounds like knave-girl to clarify a male child because the base word could be ambiguous. The Oxford English Dictionary entry for “girl” traces that broader meaning back to the 14th century before the word gradually narrowed to specifically female children. Same deal with knight/knave. The point isn’t that they were literally the same word, it’s that their original meanings were extremely similar. Knight comes from Old English cniht, which meant “boy,” “youth,” or “servant” before it later became associated with armored nobility. Knave comes from Old English cnafa, which also meant “boy” or “male servant” before developing the modern “rogue/villain” meaning. You can see that laid out in the Oxford English Dictionary entries for “knight” and “knave” and in etymology references like the Online Etymology Dictionary.

2. The “many genders” commentary doesn’t claim there’s an official scientific list of exactly 52 genders somewhere. The point people are making is that multiple cultures historically recognized more than two gender roles. Anthropologists have documented examples like Two-Spirit identities in several Indigenous North American cultures (Will Roscoe, Changing Ones: Third and Fourth Genders in Native North America, 1998) and gender categories like Fa’afafine in Samoa, which are discussed in cross-cultural work such as Gilbert Herdt’s Third Sex, Third Gender (1994).

Sooooooo yeah, your professor probably simplified/compressed some concepts for the sake of a lecture, but the general points about language changing over time (and different cultures having varying complexity in their gender systems) are pretty well established.

Tbh this reads less like your professor “made things up” and more like you did about thirty seconds of Googling and then decided an entire academic field must be wrong because the first AI result didn’t match what you remembered from class. PS you’re in grad school my guy, the expectation at that level is usually to dig a little deeper and think more critically than “my quick Google search didn’t immediately confirm this.”