They tell him that, but they pretty much picked him because shyness is what they were looking for and it showed in his demeanor from the start. It wasn't for his build, surely? He assumes it's some kind of modelling but the ad was pretty vague. Then they led him to a changing room and handed him what they wanted him to wear. Now he's just a little bit startled because voices are guiding him from nearby but he doesn't see them because of the spotlight.