@Background Pony #32ED  
Check the tag changes. Seems like the rating was changed a while back by someone who probably didn’t read the tag definitions to begin with.

So exposed genitals is questionable ?
 
Clearly visible on pinkie pie, possibly present on princess luna (difficult to confirm due to skin color).
 
Edit: Read the description for the tag but still think the rating should be higher, if not explicit then questionable+ or whatever the in between rating is.

Oh my…<3

Pinkie: The laws against public nudity have been repealed! Yipee!!!
 
Luna: I haven’t felt this free in centuries.
 
Celestia: I am glad you two are enjoying yourselves, but why was it necessary for me to join in?

The bright, shining joy of a girl who wants to share the fun of her unclothed freedom with everyone.
 
The burning determination of a princess who wants all to see as she does, to respect and follow her, safe in the knowledge that they have nothing to fear from showing a little skin.
 
The overwhelming shame of a sister who just wanted her fellow princess to get out a little, and never dreamt she would be dragged into something so utterly humiliating.