Why is the compensation for an intentional excess different from the compensation if the entire action was intentional aggression?

Primary text

The justification for awarding *Arsh* when an excess occurs beyond the measured Qisas, even if the entire original wound only mandates Diyah, is that the portion executed as Qisas was not an act of aggression (*‘udwān*); only the excess part was aggression. If that excess injury stood alone, it would necessitate the Diyah for a Mūḍiḥah. This differs from a situation where the entire action was aggression, as in that case, the whole is considered a single act of aggression.