Claire Dederer poses what in my mind is a spurious question of "why is it hard for women to write about sex?" when she makes no effort to support her supposition that it is, in fact, difficult for women to do so.
My own observations are that women have absolutely no problem talking about sex, so writing about it would be more a matter of writing skills, not psychological barriers. And I say this as someone that has worked primarily in office environments (i.e., around women) from the time I entered college to now (i.e., a substantial portion of my life); and being a person that, for some reason, women are comfortable talking around and including in their conversations.
Also, I regularly check the list of top selling "free" books on Kindle, and notice that most, if not all, of the "sexy/romantic" books are written by women. I've reached the point where, unless it is a non-fiction work, I avoid books written by women because sex seems to be emphasized all out of proportion to the story or the plot. And although I don't look through them, the covers of the women's magazines displayed at grocery stores indicate an obsession with sex.
Really, the question should be: why can't women write about something other than sex?