If you choose to earn zero and you choose to spend lots of money, you will have a higher rate.
The calculator does not include mitigating factors like pretax savings or capital investments (like houses), which offset the tax on spending.
Under the current system, when I spend savings, I do not get taxed at the 25-30% fair tax rate. You are avoiding the issue. Those who have after tax savings in certain forms (perhaps not housing, as used housing will probably see an increase in value as alternatives for taxed new housing), will be taken out and shot by this change.