You also have to acknowledge that when you have a rape accusation, there isn't a boolean result(either the allegation is false, or it's true, meaning there was rape). It's a broad spectrum, with only around a third of the cases resulting in conviction.[1]
As far as I understand, only if there wasn't a sexual contact will the allegation be considered false. In other cases, there will be some sort of investigation. So, it's possible to have basis for allegation and NOT have rape.
Correct me if I am wrong though.
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Of the 136 cases of sexual assault 8 (5.9%) were coded as false reports, 61 (44.9%) did not proceed to any prosecution or disciplinary action, 48 (35.3%) were referred for prosecution or disciplinary action, and 19 (13.9%) contained insufficient information to be coded (see Table 2).
[1]http://www.icdv.idaho.gov/conference/handouts/False-Allegati...