The intensity with which many people assert this new teaching suggests that it’s really all about justifying contraception. (It’s similar to the way so many liberal positions can be traced back to “keep abortion on demand legal.”) I don’t think all that many Christians would be eager for anal sex ... although I could be wrong, given the statistics on pornography consumption.
I'm old enough to remember when feminism was upright. Now its favorite three positions are Metania, Kneeling, and Prone.
In my case at least it has nothing to do with contraception. It has everything to do with correctly interpreting the bible.