Unfortunately, the police are not aware of all false accusations of rape. The woman might not have gone to the police but confined the accusation to the man and acquaintances. And, anyway, the cross-referencing of cases of women who have 'come to notice' is not perfect.
A strange example was of a woman who had been assaulted in a peculiarly odd manner in the course of the supposed rape. The defendant said the whole activity was consensual. Perhaps she regretted the marks or was embarrassed about them, but the case got to court, where the prosecution's opening was reported in the local paper. When the paper appeared, a man contacted the court and so the defence solicitors, to say that he had the identical experience and thought she must be the same woman who had consented. She was. He came to court and testified that the woman had consented. The defendant was acquitted.