I do not study medicin, but for language I have to actually be able to use what I memorize. Knowing how to use words is harder than it sounds, you need context. A common mistake when constructing sentences is getting the tone wrong and choosing the wrong synonyms.

Perhaps they were relying on LLMs to generate decks?

Not really. They're just stimulants. Anyway, I'm very skeptical of this use.

I'd guess uni students are buying methamphetamines them because they have gotten themselves into a situation that they cannot handle - too many non-academic scheduled activities, not enough time management skills, possibly a heavy courseload combined with several weeks of avoidance of things they found difficult, poor sleep habits, etc. They need to stay awake and work. I don't think that's all you're talking about, though.

I wouldn't discount the idea that some have an undiagnosed attention deficit problem.