I don't recognize the survey, but I wonder if the prohibition against straightline answering was not for that particular question but a series of later questions where it may have asked multiple choice where you had to answer for each soft drink that you had heard of: "Strongly Agree - Agree - Neither Agree nor Disagree - Disagree - Strongly Disagree" and then maybe the ones where you had to assign personality words that you associate with each brand or certain adjectives where they appear on a large grid of button choices.
I HATE those surveys by the way. It takes so long to legitimately answer those types of questions.
I could be way off base...