You're describing what's called an external fixator for the elbow. The idea is to allow normal motion while still protecting the joint. During the healing process, it's important to avoid compression through the joint surfaces or overload the healing soft tissues.
Without the fixator your husband would not be allowed to move at all while the bone heals. The problem with that idea is then the joint loses its motion. Regaining lost motion is even more difficult than healing fractured bones.
The rigid fixation of a pinned brace gives better control of motion. Even a small amount of torque can cause the tissues to heal with the wrong angle.