i think it is to let people know which boxes they can put the various clubs in. So when you select balls below it highlights the box that you put your balls in, that sounded bad. When you slect irons it highlights where iron sets go and when you select optional clubs like driver woods wedges etc it highlights those 5 boxes that you can put those clubs into.
I think it is an attempt to idiot proof the club selection screen. Maybe they are tired of answering support tickets of people who don't know how to equip their bag so they added this in hopes that they will get less.