He isn't saying that 100% of requirements must be understood up front, but that each stated requirement must be 100% understood by the developers. Not really un

He isn't saying that 100% of requirements must be understood up front, but that each stated requirement must be 100% understood by the developers. Not really understanding a requirement means you don't understand what the customer is asking for, and are likely to go build the wrong thing. It's a communication failure between the developer and the customer, and while I'll happily blame the customer for that, I also see it as my job to figure out what was really meant. Understanding each requirement fully does not, unfortunately, imply you know everything there is to know about the desires of the customer, but at least you are on much firmer ground than if you only barely know what you are supposed to be making in the first place.