I don't think Franks tried to "eye-gouge" Douglas per se. I doubt many players ever deliberately try to do that, and it's not really the point.
I have a big issue with Poite quite clearly shouting at Franks "Not the head" before his hands then went to Douglas' face while Poite kept watching.
My understanding is that there was a directive in recent years regarding low or zero tolerance for hands around the eye region specifically so there would be no chance of gouging, inadvertent or otherwise.
So, why does Poite warn Franks so clearly then ignore the ongoing behaviour without at least a penalty? I mean he warned Pocock about playing the ball in a ruck and then penalised because he didn't stop. Why is this different?
I can only conclude Poite is an incompetent ref who bottled it.
If they've reviewed it and Franks' actions are not deemed worthy of citing then so be it, but World Rugby looks a bit of an ass if they make gestures of wanting to stamp out certain things then conveniently forget them. But there are precedents - choke holds, straight scrum feeds were brief fads that were looked at in recent times too.
It would be interesting to see the reaction if it was, say, a Wallaby player doing it to Whitelock or Read. I mean they still boo Cooper after 6 years. Food for thought.