The wiki shows that rear_view, view_from_behind, and back_to_viewer have all been aliased to "back_turned," though the wiki itself is empty. I'm not sure this tag is being used for what makes sense. We end up with things like post #427301 being tagged as "back_turned," though I wouldn't call it that at all. Previously it seems like pretty much all of those options were covered by "from_behind," though now that has been clarified to only be used where there is sex going on and the do-er is behind the do-ee.
I would also argue that images like
post #234641
post #414294
and especially
post #189253
may all be technically images with the "back_turned," the "view_from_behind" tag makes so much more sense. I move to alias "rear_view," "back_to_viewer," and "back_turned" to "view_from_behind."
If this discussion really took place, sorry, I only did a cursory forum search and found this, but it looks like this alias just happened without really getting discussed.
Updated by Jugofthat