Hey, i just listened to this track https://www.youtube.com/watch?v=bhRIp4MVmQs, when a thought struck me.
Whoever uploaded these videos may have taken some screenshots from slinks testserver. Those that are empty of mobs show a character where the armor i think gives it away (random non matching pieces).
But then again i have no idea how hard it was to get matching pieces back then, so i may be wrong about it.