Wow; great photos Adventure Girl. I've seen similar fighting between two Cunningham's skinks, presumably males, biting each other into the base of their tails and holding fast thus forming a wrestling ring. Did you observe whether the dragons threatened each other - for instance opening their mouths - before they went into wrestling?
Yes, the dragons exhibited just that kind of ritualized fight choreography. They'd circle one another and flash bright yellow jaws, increasing speed before a swift lunge at the opponent's neck or tail. I watched multiple rounds of this dance, and neither seemed easily cowed.
Funny you mentioned the Cunningham's skinks: my partner spotted one sunning on a log, less than a meter away from the scaly gladiators. Maybe it was one of your veterans, critiquing the combat!