Very much this.

Some of the most memorable moments I had in my learning were when I "reinvented" something. In high-school, our math teacher had us reinvent the derivative rules, and later had us derive Euler's identity through Taylor Series. They were big eureka moments. Going through all the work someone else did hundreds of years ago is very inspiring, and IMO gets you in the right mindset for discovery. I can't imagine where the joy of learning comes for someone who sees learning as a test —a question, an answer, nothing in between.

In uni we built a CPU from scratch over the course of a few weeks. First building an small ALU, widening its bus, adding memory operations, etc. Beyond learning how things work, it makes you wonder how inventing this without a teacher to guide you must've been, and gives you an appreciation for it. It also makes you extrapolate and think about the things that haven't been invented or discovered yet.

In theory LLMs could serve as a teacher guiding you as you reinvent things. In practice, people just get the answer and move on. A person with experience teaching, who sees how you're walking the path and compares it to how they walked theirs, will know when to give you an answer and when to have you find it yourself.

One doesn't learn how to do lab-work in the library.