Keep in mind that A. A. Milne, who wrote Winnie the Pooh, was born in 1882.

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This reddit thread gathers some information that chapters starting with "In Which Our Hero Goes To Have a Tea Party" etc etc. is a style from the 1700s and 1800s.

https://www.reddit.com/r/whatstheword/comments/8t9hjr/wtw_for_chapter_titles_that_all_start_with_in/

When he had stories read to him as a child, they could have easily been from the 1700s, like Winnie The Pooh, Sherlock Holmes, The Wind in the Willows, and A Christmas Carol are read to us and are over 100 years old now. When he wrote chapters in Pooh that describe the plot in the chapter title, he was probably doing it as a sort of quaint throwback to his own childhood reading. When it bothered you in your childhood, you were reacting to a nearly three hundred year old writing trope.