Did you just sit there in class and then never do anything with what you learned afterwards? That certainly isn't how I approached university.

Doing something with the knowledge given in a lecture is very distinct from fact checking it

I'd say it's a subset of fact checking it. You can check facts without doing anything else, but doing something with the knowledge is inherently checking it. If the lecture presents some programming technique, and I implement it, I'll find out pretty quickly if it's wrong.