A legitimate (bona fide) rape leaves physical evidence that is not generated during consensual intercourse. When a woman's reproductive organs are physically damaged, that is fairly strong corroboration of her claim of being raped.
Shades of Akins.
There are quite a number of women who enjoy highly vigorous intercourse. And even quite a few who are into being on the receiving end of the whips and chains bit.
I sincerely doubt there is any physical evidence method to distinguish between such activities indulged in consensually, and those where participation was forced.
Also, the instrument (ahem) used to damage the female’s reproductive organs is not (usually) a 2x4. I suspect it’s difficult for a rapist to do all that much damage without damaging himself in the process.