The questions that you identified as "control" questions are actually irrelevant questions and are not scored. On the other hand, unless there has been an unannounced policy change at the FBI, the question about your drinking habits was a probable-lie "control" question, deliberately intended to create a response even in people who are truthful with regard to the relevant questions (e.g., illegal drug use). During my FBI pre-employment polygraph examination, I was asked whether I had ever driven while under the influence of alcohol. That, too, was a probable-lie "control" question (but a very poor one, in my case). If you told your polygrapher that you regularly serve as a designated driver, then perhaps he chose to forgo using the more commonly asked "control" question about driving while under the influence of alcohol and instead to ask you this more general question about your drinking habits.

May I ask whether your background investigation was otherwise complete before your polygraph examination? The reason I ask is that a former FBI agent (coincidentally the one who administered my FBI polygraph examination) recently stated that the polygraph is the last step of the FBI's hiring process, which if true, is a new policy.