Mr. Young exaggerates, but not by much - but that's not an argument against world-building, more an injunction to think about broad structure and logic of the world more than minutae, because without those, when the players veer off the map you have absolutely nothing to fall back on. Further, it's worth developing some of the serious powers of the setting to decide what's going to clobber the players when they do stupid things. World-build for the unexpected.