The point being that vastly superior mil tech has definitely allowed smaller armies to decimate larger ones. Besides which, I've never seen a 1-stack take out a 50-stack regardless of mil tech level, generals, or any other advantage. That's obviously a huge exaggeration. If a Western 20-stack takes out a Chinese 50-stack with a 5 or 6 mil tech level advantage, I'd say that's entirely plausible.
The thing is though, it isn't an exaggeration. Did you ever play the earlier versions of the game? I conquered all of asia with 1k men in the late game as a European nation.