Graham is short. That doesn't excuse a high tackle, but it does give Frank a bit of leeway imo. Pritchard was tackling him as he would any other player coming towards him like that. Rugby league is a fast paced game. It's easy for us on the sidelines to say he could've moved down or adjusted but under fatigue, filled with adrenalin and the defence coming towards him at pace, do you really think 'better duck down a little bit here just in case' crossed his mind? Of course not, but I'm sure 'I can get a big shot here on Wade' did.
High is high I agree, regardless of the situation. But a penalty would have been sufficient, it's not worth getting suspended over.