It's pretty hard, but I don't think it's a 1 frame techtrap. Imo this whole setup is a waste of time actually. Why put so much effort in this if you will only land it once or twice (if you're lucky) in VS. After that be sure that your opponent will never hold [G] after WP 1B+K. I have never gotten SS to work. I'm not sure why. Also, the timing for CS varies for each character due to hitbox differences, I think it's the main reason why all this is worthless outside of practice mode =/
Out of all characters, I think it's fairly easy to land this on Astaroth. For example: CL A+B,A+K, WP1 [B+K], iCS. Do the first A+B,A+K part normally, and then WP 1B+K, where you hold [B+K] to the end. She will then glow blue twice. The first glow will occur when you press WP 1B+K, the second one is important, because it occurs at the same time when the recovery of WP 1B+K ends and when she enters SW. That's when you just time your 1+A+G. She will do iCS at the same moment when she enters SW.
Overall it's not easy, but it's still nowhere near SC3's VC SS or FC 1B -> throw, in terms of difficulty. That was the most crazy shit ever. I have never done these two in VS, and the latter one I couldn't even do in practice.