You have said it "doesn't matter", meaning you believe the Pentagon would have been hit "anyway", as though Rumsfeld had been aware of some exact predestined schedule, with all variables known, including a known number of planes, and behaved accordingly.
Needless to say, that doesn't make sense.
Beyond the fact that the suggestion drifts into a territory that we cannot know, unlike the rest of our fact-based discussion, it is also completely irrelevant to the topic of Rumsfeld's willful failure to act toward reducing the chance for further bloodshed.
Perhaps he thought people could protect themselves from crashing planes(?).