Forgive the nitpicking, but yes, it is. Nicotine is a drug.
Edit: This isn't advocacy for Apple's decision to ban the apps; I think that's silly (and I also think vaping is silly) and likely to have about zero impact. And if it does happen to reduce vaping use, that's probably bad for public health, because vaping looks so far to be less harmful than cigarette smoking. When vaping products are banned (not by Apple; I'm talking governments here), cigarette usage is likely to go up.
My unsolicited advice: Don't smoke. Don't vape. But if you must do one of the two, vape instead of smoke. And use legal vaping products, provided they still exist.