I am not saying the women do it 'just to get back'. I'm sure they sincerely believe they have been raped. But the court finds they weren't raped.
That said, there are well-proven cases of women making up false accusations of rape. There are various reasons. Sometimes it is to get back at someone, but other reasons are attention-seeking or because they don't want their boyfriend/husband to know that they were willing partners. But this is really a separate issue.
I repeat my fundamental point to men. ONS are just too dangerous in the current climate. It may seem like a good idea in the heat of the moment, but you're laying yourself wide open.