The February bombing of Darwin did not come from an entirely unknown fleet threat. Allied authorities knew that a Japanese naval operation was developing, but historically had no organized force able to respond. A surviving ABDA command and concentrated fleet give that warning an operational purpose. The counterfactual changes the ability to act on intelligence rather than assuming perfect foreknowledge.
Notable Point · 1:09:17-1:09:32
Darwin had warning but no fleet to act on it
Allied awareness of a Japanese fleet operation did not produce an organized force capable of interception.