That's fine amd dandy from a US perspective, but many European universities are different. I don't know about this guy's exact class, but some (many?) undergrad classes are 500 people in a lecture hall with the professor orating, no textbook, and the content on the exam is pretty much whatever was covered during the lectures. So accurate note taking is very important because those notes essentially are your textbook. Hence the small business of students assembling high quality lecture notes and selling them to people who have't been to class (much).

It does not make too much sense to compare textbooks and class notes, specially when you get to higher level classes where the textbooks are reference textbooks, hardly readable by someone who is not already familiar with the material.

Your study notes will contain parts of the textbook, of course, but also explanations that are not in the book, maybe examples that you find useful and that might not be in the book, counterexamples, doubts, schematics... No textbook will have 100% of the contents you need to study.

>A textbook is an infinitely better reference than any notes one could take in class.

but...

>Ask all the small, nuanced questions that you can think of in the moment, which you can’t find answers to easily online or in the book.

and then what, forget them by the time you go back to the book? Why was the book so good again if it doesn't answer all the questions? It makes more sense to record the answer to those useful questions you ask, maybe in the form of some notes.