I think there was a comment about him apparently crapping himself when Senior faced up to him. I'm guessing he's probably a few stone heavier than Senior but there are just some Backs you just don't mess with be they G.I., Senior or 'Scrappy Doo'. So, fair play to him on that front.
I'm not Graham's biggest fan, but he would go well down in Oz. He would possibly have to change his game slightly but he is clever and tough enough to do that.
With regards to him bottling it, perhaps he just didn't want to get binned. These days you rarely see players stand up and fight as it will inevitably end up with them having a 10m break. That doesn't mean that these players are cowards or bottling it, they are probably being pretty sensible.