The voltage at the sense pin (VIs) is not internally clamped and thus it may rise to very close to Vs (Supply) voltage depending on the Isense current (Iis) and the resistor (Ris) on the Is pin.
In normal operation (no fault conditions) the Iis current is proportional to the Iload current and this linear relationship is specified in the datasheet as long as the Vis<Vout-5V. When VIs > Vout-5V, there will still be sense current, but less likely to be linear as compared to load current.
During Fault Conditions again, we need this 5V differential voltage between Isense pin and Vs(supply) for full fault current to flow. This fault current would be lower if the above differential is less.
