Maybe we're speaking in two different languages. When I'm referring to frames, I mean the frames of animation... essentially the speed of the attack. A 5 frame attack would be twice the speed of a jab in Tekken 6. If what we saw in that video was 3-5 frames, you literally would not see Sub-Zero's hands move. I clearly saw his hands move, and stop... then the freeze occured. That's why I guessed ~20 frames.
In theory, a larger active window gives you more time to punish, but without knowing the speed of most attacks in the game, that's only theory. For all we know, the fastest uncounterable attack could be 15 frames. That only gives you 5 frames to react to the counter and still hit Sub-Zero (not counting recovery frames). Even if you bump that up to reacting in 10 frames, that's pretty fast. That's like ducking a jab in Tekken 6 on reaction. I don't know anyone who can react that quickly.
I would say you'd need at least ~15 frames for the top players to react to something. So if the fastest punishment is 15 frames (again, just a guess), the entire counter would need to be 30 frames (execution, active frames and recovery) for the best of the best to punish it... and they'd still probably miss it a few times.