Tomahawk mini-ITX USB 2.0 header

hi all - first time builder here with a quick question: the Tomahawk mini-ITX comes with an extra USB 2.0 header cable that I'm not exactly sure what the purpose is. The user guide only refers to I/O's being the USB 3.1 gen2 and USB 3.0 available in most modern motherboards (referring here to "Installation Guide" page 3). Is the purpose of the USB 2 header to be able to use the front 3.0 usb ports as a 2.0? Otherwise, can you please advise what the purpose is? If no use, is it worth finding a cover to avoid dusting or other issues with a loose cable? cheers