It should be clarified that the advice is to purchase short-dated Treasuries, which have negligible exposure to short term volatility (and are typically the place people park money in times of distress).
Also, an important note is that none of the major banks in the US pay 4% or anywhere near that amount on deposits. Think 0.01%.
Long term bonds, as you correctly point out are extremely sensitive to changes in interest rates.
In the current (rather unusual) situation, where deposits pay nothing and short term Treasuries pay reasonably well, this advice is sound.
Also, an important note is that none of the major banks in the US pay 4% or anywhere near that amount on deposits. Think 0.01%.
Long term bonds, as you correctly point out are extremely sensitive to changes in interest rates.
In the current (rather unusual) situation, where deposits pay nothing and short term Treasuries pay reasonably well, this advice is sound.