Actually he thinks everything about the way we tax savings is silly.
Here's the key graph from the talk Ken Henry delivered today in Adelaide:

Super contributions are negatively taxed, big time. Rental properties and shares are also negatively taxed big-time, but only if they are funded by debt.
Make sense?
Meanwhile savings parked in bank accounts are taxed massively - at way above the saver's marginal tax rate.
Make sense?
Hold on.
This speech throws the lot into the mix.