I worked at a small company once and they were really excited because they were going to get health insurance! It didn't affect me, though, b/c I was covered under DH's policy at his work. So I didn't answer any of the very personal questions on the form, or even turn the form in. Then the boss came back to me and said 'we need you to fill this out'. Again, I declined. This was my personal medical information, and I was NOT going to give it out because I was NOT going to use their insurance. Then boss came back AGAIN and said that they needed me to fill it out, just b/c I was employed there, and they had to have forms from everyone as proof of how many people they employed, regardless of whether or not the employee was going to use the insurance. I was not happy.
I doubt it's exactly like that, since you're government, but it could be something similarly weird (although the personal nature of the questions does give me pause...)
I still wouldn't fill it out though.