It doesn't appear to me that archers present much of a deterrent to rushing.
Without knowing what exactly happened there, I can guess that archers were shooting each other for quite some time (as most players picked 4 SA), and after melee started they could naturally continue providing missile support by targeting neglected units. This is an advantage compared to guns, who cannot perform this second function, but teppos can be more influential in the battle as a whole. They might score less kills but the morale penalties they inflict makes them a more reliable deterrent to rushing.