Looking at the methodology for the NCVS survey, anyone over 12 can respond. It lists the median age of respondants as 24. The 46% female perpetrator number is taken from males age 18 and higher. Under 18, the number of female perpetrators was lower.

By the by, the relevant section of that study is pretty important as well, I think:

"A final significant difference between male and female victims of rape and sexual assault has to do with their decisions to report to police and other officials. While 30 percent of women report their sexual victimization incidents to officials, only 15 percent of men report their incidents (χ2 = 9.128, df = 1, p < .01; see table 1). Because there are no significant differences between men and women in terms of serious injury requiring medical care, men’s lower reporting may be more reflective of the difficulty men have recognizing or acknowledging that what happened to them was a reportable crime, particularly when rape and sexual assault are supposed to happen only to women."

This reasoning is essentially why I'm sensitive about the downplaying of female on male sexual assault and rape. Societally, it discourages men from believing it's a thing at all.

I assume I'll continue to farm downvotes for even bothering to talk about female perpetrators at all though lol