This isn't a good measure of proficiency. I frequently do both of those things---in fact, I consider it a bad thing when someone does not, because that means that they are not exploring others' solutions to the problem, or learning other methods of doing something. Struggling is a good way to learn, but at some point you should see what others are thinking, and how they are doing it better than you are.
Similarly, manuals (manpages, info manuals, online resources, etc) are essential: trying to memorize every detail when certain things aren't often used is not an efficient use of one's time, and that knowledge will only fade unless applied.
I think the point you were trying to get at was that for what was taught in your course, the students were proficient enough that they didn't need to reference other resources.