That stuff IS true. There was once a point in time when people (well, native africans) thought there were no female hyenas. Not only do they have a pseudo-penis but also a pair of false testes (it's actually just two balls of fat).
Female hyena are also the dominant sex. The biggest and baddest female is the leader of the "clan". She gets to have any male she wants and the other hyenas (both males and females) must suck on her pseudo-penis to show respect. The lesser females also dominate their respective males in that way.
That's the extent of it though, their peculiar member doesn't get hard for penetration (as much as futafags want to believe) since it's more like a fleshy tube and, in fact, folds inward to function as a regular vagina when the time comes (and so do they).
Also, for some reason, this is all exclusive to the Spotted Hyena. Other hyena species follow the same gender roles as the rest of us mammals.