> For women, answering the questions is voluntary, as they cannot be required to perform military service under the Constitution.

Specially article 12a Paragraph 4: https://www.gesetze-im-internet.de/englisch_gg/englisch_gg.h...

Specifically it says:

If, during a state of defence, the need for civilian services in the civilian health system or in stationary military hospitals cannot be met on a voluntary basis, women between the age of eighteen and fifty-five may be called upon to render such services by or pursuant to a law. Under no circumstances may they be required to render service involving the use of arms.