When I used gender nutral pronouns, the sentence would be "They are in their bed." If I only swapped the pronoun, the sentence would read "He are in his bed"
So I had to manually read through all 130k words to fix all of the sentences to "He is in his bed". Some sentences were "They ran through the forest", which would swap to "He ran through the forest", which was fine. That's why I couldn't just mass update and be done.