Tried the main addon site from back then is gone and replaced completely. But I know KoS list existed in Vanilla. This was to prove these addons have existed long before classic and its not NEWLY added just for classic.
Of course it matters that dates that are supposed to prove that something existed in Vanilla are actually dates that apply to Vanilla. Whether it matters when it comes to the addon being in Classic is a whole other topic.
Back in vanilla, I had my very own addon that was very simple variation of Spy. It was very easy to code it. And im pretty sure there was public KoS addon.
I really have no reason to doubt that. It would be weird if it was impossible to make a Spy like addon in Vanilla. My only objection to this thread is that nothing here proves that for a fact yet the OP presents this as if he had proven it.