I really don't like Penrith, but gees they are a mentally tough squad. Their ability to absorb pressure, stay in the game and then turn momentum is second-to-none. When they're on, to beat them you really need to get a big lead - 18+ before you can even contemplate holding on.
Parra are lucky - a good completion rate is keeping them in the game and they've thrown three or four passes that could well have turned over possession. Gutherson passes less than Tedesco, well maybe not but there wouldn't be much in it.