When we do abseiling with your dogs they ALWAYS wear a muzzle, even if the dog has never bite anyone, has done this 100 times before and could take a nape during a zip-line. BUT... the less thing you want is the dog freaking at last minute and taking a bite to the rope, the harness, the parachute lines or wathever. If there is a 0,001 percent of possibilities of it happening, we don't take it.
cant speak for that specific dog but one of my old high school friends is a Seal in the dog program. Some of the dogs are taught to go for the throat opposed to limbs and those dogs are muzzled while wearing gear (work mode) unless they are just with their handler or on assignment.