Yes, that wasn't unnatural at all, to have Tenma's older sister suddenly give a lecture on how sugar is made, when baking a cake. It's weird how Japan is such a high tech country, but it doesn't visit the author's mind that a dude could be randomly surfing Youtube and come up with a video explaining how sugar is made. Youtube is all the time suggesting videos of all kinds to people, following past behavior but also utterly randomly. If the author is against technology, make the dude read a popular science magazine. Why not a bloody school history book.