According to the FMI 3.0 standard, in Event Mode fmi3Get{VariableType} computes f_event (s. 2.3.5. State: Event Mode).
When fmi3UpdateDiscreteStates() is called and f_event is already computed (i.e., fmi3Get{VariableType} was called before), fmi3UpdateDiscreteStates() only computes the time of the next time event and Clock ticks.

In Stair.fmu:
When fmi3GetInt32() is called in Event Mode, only the old value is returned without triggering the computation of f_event. The computation is performed in fmi3UpdateDiscreteStates(). If the importer does not call fmi3GetInt32() again, it does not receive the updated data in this Event Mode.