I don't think they are checking. I think is is a standard survey question.

In some of the surveys I have received, a question asks something like "Have you taken a survey/completed market research in the past 3 months about booze/restaurants/TV shows/etc..." - I have always answered "NO" (even if I had ). There has never been a problem.

All these surveys may or may not have been e-rewards. (I forget - some may have been HI Points or some thing else.) But I have always received credit!