He's entitled to stop a fight if the fighter is "unable to continue." But it is considered by the commission (and should be) very unseemly to stop the fight due to a cut without consulting the physician.
Just point of fact, the referee is fully vested to make the determination whether a fighter is able to continue, no doctor is required for that. He may, if he wishes, call the doctor in to evaluate the injury but that is not required to stop a fight (or deduct a point or DQ).
Of course, Mazzagatti didn't stop the fight because of the cut (which was caused by the elbow).
He stopped the fight because of Hamill stated that he could no longer continue (because of his arm, which was absolutely not caused by the elbow).
Mazzagatti was perfectly within his power to stop the fight. I'm glad he stopped the fight.
However, he's not entitled to declare the fight a DQ win for Matt Hamill without a justification that the injury which ended the fight was caused by an illegal strike (which it clearly wasn't).
I'm annoyed with this, because I've already made this argument in a handful of individual posts on this thread (as well as in the initial article) and you clearly didn't read it before commenting.