I did some rapid web searches to dig in here because I was curious about how this might be abused. It turns out that is better worded than it would at first appear. I think the trick here is it depends on whose definition of “depressant, stimulant, narcotic” you go by.
For example, the CDC considers caffeine a stimulant, but the FDA says it’s a “food additive”. So there’s no FDA schedule for caffeine, which means you also can’t get a prescription for caffeine pills, nor pay for them through insurance. But that also means it’s arguably not a drug or “stimulant” under this definition.
Meanwhile, alcohol labeling is handled by the FDA, but it looks like everything about the substance itself falls under the ATF (it’s in the name after all). The ATF seems to take great care to not categorize alcohol as a depressant and goes out of its way to never call alcohol a “drug” (example). And, as it turns out, (Federally) alcohol is not a controlled substance.