Whilst the analysis is fun, it feels like he misses the point. He does it because he can.
It should be of little surprise to learn that Bryan is wearing shorts because he prefers wearing shorts to wearing trousers - that's obvious. What I find more interesting is to look at the conditions that allow him to do as he chooses.
In academia people are insulated from the types of norms and custom that predirect your attire. The reason as to why I tutor in an Everton shirt is not because I like to express my support (even after this), because when I worked at Swiss Life - and was just as much of an Evertonian - I wore a shirt and tie.
The fact that it maximizes his utility is largely irrelevent, he does it because he can.