One of the problems with parents asking this question and taking the answer at face value is that not everyone defines the word “sex” equally. Many teenagers understand sex the same way Bill Clinton did. There is even a strong contingent of teenagers who define sex so narrowly that it only includes vaginal/penile intercourse. Many parents understand sex to be a much broader term, and would almost certainly include any kind of oral or manual stimulation in their definition.
So if parents really want to know the answer to the question “Are you having sex?,” they will have to get much more specific. But it’s a rare parent who is willing to get much more specific than that. And, let’s be honest, it’s an even rarer teenager who would be willing to hear their parent utter the words “oral sex” and actually answer their question.