You could have a setup where the other end of the USB cable is hard to reach so you can use the circular connector to swap the keyboard-side of the cable for a

You could have a setup where the other end of the USB cable is hard to reach so you can use the circular connector to swap the keyboard-side of the cable for a different style USB connector. But then why not just have a USB extender mounted to the desk in an easy to get to spot? You would need to make a bunch of variations of the USB to circular connector pigtails to plug into the main one. Seems like a lot of work for something that usually only takes a couple seconds if you have an easier to reach USB port. If the guy says the circular connector is just decorative, I'd believe him. Nothing else really makes sense.