Start with the code, and create your levels around the code. You'll have to do that anyway, but starting with design will result in design -> code -> redesign.
HORRIBLE advice.
To rephrase your quote:...but starting with code will result in code-> design -> recode.
Example 1: you code a level. You realize late in the coding that you need a day/night system. Now I ask you, how hard will it be to recode the game to include a system that wasn't included in your original code?
Example 2: you design a level. You realize late in the design that your levels need a day/night system. Same question: how hard will it be to redesign your document to include an day/night system?
