They do not have the opposition reflex when the pressure is directed toward the bridge of the nose. A dominant dog will seize the submissive dog by the muzzle to emphasize its rank. You are gently expressing dominance. The spot immediately between the eyes is a calming acupuncture pressure point so some dogs calm down just because you put the halter on. This is a totally new sensation for most dogs and they will need to be taught to accept the head halter.
Dominant dogs tend to object the most.
There is danger to your dog if you jerk on the lead attached to a head halter. Consult your veterinarian. There is danger if a dog is left unattended with the head halter on. There is too much risk of objects being tangled in the halter. People who have never seen a halter before will assume it is a muzzle.