Jason Zweig is one of the best finance writers out there. I do have slight quibble with this:

One popular rule of thumb is that you will have to cover only 70% to 80% of your pre-retirement spending. (Another version says you will need to replace about the same amount of your pre-retirement income.)

I've typically heard a hybrid of those: you will need to replace 80% of your pre-retirement income. That make sense because if you on are track to FIRE or even RE comfortably you necessarily need to have a high savings rate, on the order of 15-20%. In retirement taxes drop typically significantly do to favorable treatment of capital gains and retirement accounts and lack of FICA.

Since you are no longer saving and one of your biggest expenses is reduced, so the need for income is also reduced. Spending is controllable too. The article quoted a gentleman who wound up spending just as much as he did when he was working because he was out doing things. That's a choice. You can spend more in retirement if you like, but you have to work longer.