Breaking glass physically disrupts the unity of a solid object. Openly communicating a command does not involve literal shattered glass; what is removed is the condition of concealment.
The metaphor must not be reduced to merely speaking at high volume. It concerns unreserved, manifest, effective proclamation. The energy of a sensory action is transferred to a conceptual act of communication.
The fact that both expressions can appear as verbs does not make their underlying meanings belong to the same class. Their sensory or conceptual status must be considered separately.