And not the only inaccuracy...
5.5 inches = 15 centimeters
Actually 5.5 inches is 13.97 centimeters.
And yes, if women could only take 5.5 inches without hitting their cervix I would have either hit a lot more cervices or not been able to completely enter my partners. However, thus far, I have only hit 1 woman's cervix, and then only by thrusting hard and being extremely hard at the time (so it was considerably deeper than 5.5").
But what bothers me most, and this has been true since I was young, is the arrogance of people, men and women, claiming to speak on behalf of their gender. I remember a seeing a woman on tv when I was in high school talking about how women could only have orgasms through clitoral stimulation. Thankfully I chose not to assume that was true for all women (or some of my partners would have been extremely unhappy and disappointed).
So while "Zanucky" can feel free to speak for herself (though I'm sure her condition is not unique), she should not be so arrogant to speak for other women. And if she can only take 5.5 inches inside of her then, frankly, I feel a little sorry for her though I hope her beliefs attract a partner who benefits from them.