Was it legal to round people up like that without even probable cause before the war? Current law can be changed and even constitutions ignored when it becomes convenient.

Maybe those committing fraud believe that if they NEVER disclose something, its pretty much a sure thing that it can never be used against them.

You might be able to convince me that at least one person lied on the census, but you will have a very hard time convincing me that even 10% of the dead/moved eldery had somebody lie to the census about their existance. I find it far more likely that most of these people are a series of clerical errors.

I wouldn't try to convince you that dead people did anything.

The government changed the law to allow previously private information to be used for new purposes. They could do this again.

The only way you can prevent the government from misusing information is not to give it to them.