And what exactly is stopping the opponent from just teching the knockdown and rolling?
ok, so ive found a concrete way out of the set up. simply tech rolling is not enough, as you roll right into scorp, but you can techroll, then wake up, which gives you back your invul frames and lets you escape. i wouldnt suggest exclusively using this set up, but i assure you the first time this happens and the port whiffs, your opponents reaction is not "better tech to wake up" its more than likely oo he whiffed the port, now i can punish.
additionally, the timing is a bit strict on teching that knock down, as its not clear when you are able to begin the tech to get out, and if you whiff the tech then you just fucked up your blocking too
However, if you know your opponent is gonna tech roll and wake up, you can MB f3 which will armor through the wake up, and you have time to confirm it because youll see the rolling animation before the special comes out.
Edit: seems that depending which combo you use can actually change which side of scorpion the opponent will end up on after the tech roll, so they will have to have extensive knowledge of the set up to know which way to tech and then wake up in order to escape it