Many things are more invasive than that. The insertion of a needle into a human body, for example, would undoubtedly be more invasive.
However, even if it isn't very invasive, the very fact of having to answer, and of being subjected to the procedure when one has not done anything wrong and there is no suspicion, is invasive. It's like having to go through an X-ray machine at an airport, for example. In both cases, there is no direct intervention on the human body—something which, absent judicial authorization, would constitute assault.