I’m not a moderator, so I hope it’s okay for me to weigh in on this…
For modern cartoons, Friendship Is Magic itself made references to R-rated media that were definitely meant to fly over the kids’ heads and amuse their parents:
- In “Look Before You Sleep”, Twilight’s book Everything You Ever Wanted to Know about Slumber Parties (But Were Afraid to Ask) references the Woody Allen film Everything You Ever Wanted to Know about Sex (But Were Afraid to Ask).
- In “Make New Friends But Keep Discord”, the shot of the Smooze flooding out of the closet is a clear homage to a scene from The Shining.
- In “Every Little Thing She Does”, the picture of Big Macintosh using mud to hide from a monster is a reference to the first Predator movie.
The general rule seems to be that if something requires outside knowledge to become dirty or adult, then it’s still okay to include in children’s media as a bonus for parents watching.
And I’d say the pole dancing in your linked pic falls into that category. The pony isn’t posing provocatively, and she isn’t drawn with any naughty bits to show off. All she’s doing is spinning around a pole, and twirling in place a bit. It requires outside knowledge (namely the fact that strippers typically pole-dance) to make anything about it seem dirty. So I think that’s why it’s considered “safe”.