It sounds to me that he mixed styles and over did each. His shirt is what most of us would see as very casual. But every thing else was very formal. From the belt down he is dressed semi-formal for a casual affair and the shirt is semi-casual.

As you said it sounds like he purchase a kilt package with out understanding the time to wear each piece.

Picture someone in old sneakers, no socks, aged jeans, a wide western belt and a tux jacket, tux shirt and bow tie. There would be a disconnect even though each item is acceptable.