The explanation for what you saw with the 5 moving in a line is that they spread out using their "spread formation" keys and then pressed the one key they bound to move them all forward.

Most of us will setup our main WASD/etc. style movement keys for use on our mains which are NOT bound on our alts. Then we'll setup another set of movement keys so that EVERYONE uses those, like the arrow keys or keypad up/down/left/right, which gives us the ability to /follow for most situations and then switch to "group individual movement" when needed.