I have no idea about current textbooks. But certainly the physics textbook that I learned from quoted the myth. And it is easy to find examples online, like htt

I have no idea about current textbooks. But certainly the physics textbook that I learned from quoted the myth. And it is easy to find examples online, like https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Map%3A_Physical_Chemistry_for_the_Biosciences_(Chang)/11%3A_Quantum_Mechanics_and_Atomic_Structure/11.02%3A_Planck's_Quantum_Theory https://chem.libretexts.org/Bookshelves/Physical_and_Theoret..., that still do. I wish it were otherwise, but there are some weird dynamics in the textbook industry that reward looking like other textbooks more than accuracy and usefulness. A classic essay showing this is "The Case of the Creeping Fox Terrier Clone" in Gould's book Bully for Brontosaurus" that traces the history of textbooks comparing Hyracotherium* to a fox terrier. This, despite the fact that most students and authors have absolutely no real idea how big a fox terrier is. And it wouldn't help if they did know, given that Hyracotherium actually weighed over twice as much! Another classic essay showing how textbooks repeat other textbooks without properly questioning what should be taught is https://web.williams.edu/Mathematics/lg5/Rota.pdf https://web.williams.edu/Mathematics/lg5/Rota.pdf. If you've taken some variant of the differential equations course that he discusses, I highly recommend reading his essay. I guarantee that it is far from the only standard course with such levels of silliness.