i think this is for the scenario where you have uncomplicated acute appendicitis that can be treated in time.

there can still be scenarios where you developed acute appendicitis, it isn't treated in time (by either surgery or antibiotics), it perforates, possibly causing "infection of the lining of the abdominal cavity"

so i'd guess that removing the thing before there are any symptoms would still reduce risk, although maybe the cost-benefit tradeoff is a bit less clear.