You should only use this option on machines which have USB bugs - for most machines it's not needed (as the training material says). It's designed for machines with buggy BIOS code.
I don't believe the "always enable USB" option is generally tested against all hardware - it's only tested in the case where the automatic enabling does not work.
And since most modern machines are now UEFI, it's becoming less relevant anyway. (UEFI machines have their own built-in USB support).