It has incredible bearing. Let's presume it took him 1 hour to design the site. (It surely took dozens or hundreds, including modifications and improvements, but play along.) That 1 hour isn't just 1 hour. It's 1 hour, plus the 5 or 10 or 15 years he has spent living and breathing design, refining his abilities and sharpening his understanding of the craft. He can do a singular design faster than a "layman" because he has spent a significantly greater amount of time on Design in general.