In Sweden you have to reply if you agree as well, because otherwise they could never convict someone of tax fraud if the pre-computed data is missing some of your income, for example. (Well, maybe they could convict you, but it would be hard to defend that morally when they didn't even force you to acknowledge the numbers.)

Why would that be true? Law: "Thou shalt inform the government about finances that affect tax, or else be heavily fined or put in prison when we find out." No need to have this information duty tied up to the tax return.