On him meeting a potential wife with a chaperone the wife will be in hijaab (loose fitting clothes) with her face and hands on view as this is all that is allowed. Now if he would prefer a wife with a large chest (he is entitled to this) how would he know for sure? To ask her or her relatives would be out of place. The only thing I can think of is that in front of his female relatives she can take off her abaya or jilbab and they could get a better "assessment". Otherwise what else could he get this "information"? This is a serious question!