feminists citing studies on sexual assault on campus
To talk about the prevalence of sexual assault on campus, surely? If I want to talk about the prevalence of off-campus sexual offending, I would use studies about off-campus offending.
most of the women classed as being 'raped' didn't actually know it themselves
It is distressingly commonplace, both amongst rapists [1] and victims, not to use the word "rape" to describe acts that meet the criminal definition of the word [2]. A woman who tells her husband no but he puts his dick in her anyway is unlikely to describe him as a rapist nor herself as a rape victim, nonetheless he is a rapist and she has been raped. He is unlikely to describe himself as a rapist because of commonly-held, and legally-unsupported since 1992, beliefs about rape within established relationships.
Studies are designed to measure whether men have actually raped, not whether they label themselves rapists nor whether their victims label themselves as raped. Asking questions that describe events and behaviours, instead of labelling them as "rape" without further description, is by design to get accurate results.
Footnotes:
[1] If a survey asks men, for example, if they ever "had sexual intercourse with somone, even though they did not want to, because they were too intoxicated (on alcohol or drugs) to resist your sexual advances," some of them will say yes, as long as the questions don’t use the “R” word.
Emphasis mine.
[2] Section 1: Rape:
(1) A person (A) commits an offence if—
(a) he intentionally penetrates the vagina, anus or mouth of another person (B) with his penis,
(b) B does not consent to the penetration, and
(c) A does not reasonably believe that B consents.
Note: nowhere does it say "(d) unless B was drinking", "(d) unless A and B" are dating", "(d) unless A is B's husband" etc.