> the current phase of thinking someone has to be of a group to understand the group is wrong.

> Or maybe men and women are even more similar than I'm accounting for and a young woman's journey is just that similar to a man's

You're almost there; the point is not that you have to be in a group to understand a group, but that because of the power structure some are much more visible and celebrated than others. A female writer is more likely to be able to see what the male journey is like (due to thousands of examples) than a male writer, who is in turn more likely to project his own prejudices than actually find out what it might be like.

(In turn, there have been a number of literary fights lately about white female authors doing terribly bad racial stereotypes of their nonwhite characters...)