Airbus was asked this question,
The aim of the inner tank split valve is to separate the forward and aft parts of the inner tank in the case of an engine rotor burst. According to the test results, if the engine is damaged and the engine rotor bursts, some pieces of rotors will most likely to affect the forward part of the corresponding inner tank. As a result, the inner tank split valve allows an isolation of the forward part of the inner tank, and saves the fuel in the aft part of the inner tank.
There are cases that the inner tank split valves should be isolated. When the engine is damaged, the flight crew has to apply the ENG 1(2) FAIL procedure and close the split valve on each side, as stated as the “L+R INR TK SPLIT.........ON” action line in the ENG 1(2) FAIL procedure.
Therefore, we would like to inform that the fuel leak procedure does not directly require closing the inner tank split valves, as the probability of having a wing fuel leak that does not result from an engine rotor burst is extremely low.
In case of structural leak, the “ENG 1(2) FAIL” ECAM warning will always trigger, asking the flight crew to split the inner tanks. In the “FUEL LEAK” paper procedure, in the “CASE 1: IF ONE INNER TANK DEPLETES FASTER THAN THE OTHER BY AT LEAST 500 KG (1 100 lb) IN LESS THAN 30 MIN”, it states that if the leak continues after engine shutdown, a leak from the wing may be suspected. In this case, the leak from the wing can be due to transfer valves failures. In such a failure case, there is no benefit to split the two parts of the inner tanks.