Albert and Fiona Dietrich argued for a long time, should the boy become a frontbender or a backbender, as Albert himself was specializing in frontbends, while Fiona was a backbending expert.
It was a hard choice since the boy's unique flexibility in the hips could make him a legend at frontbending or backbending, but he'd most likely stay mediocre if they went both ways at once. In the end Fiona won because she didn't have her own "number 1" pupil, while Albert already had Natalya, his "number 1" student:
So after this argument, both agreed it's only fair to go with backbending. Since then Fiona would spend 2 hours a day exclusively with Andrzej and the boy progressed so rapidly that soon Albert also had to join to help around with stretching as Andrzej literally became difficult to handle for just one trainer.
Andrzej himself was really happy with all the things he was taught to do, he was born with double jointed legs and always loved playing around with them even before he met the Dietrichs, but now that his back was also flexible... oh boy, he couldn't get enough of the cuddly feeling of having his butt sitting on his own upper back. At first it was very exciting but at the same time made his spinal column and chest feel so tense, so it was very annoying, but week after week it became easier and in the end he couldn't feel his backbone at all, just like in any normal pose.
The triplefold became so usual that Andrzej grew to like falling asleep in that pose because it was so warm and comfy and for some reason sleeping in a triplefold always gave him very pleasant dreams.