Der Joe,

so without using the word "longitudinal axis" and other sophisticated stuff.

Christians waza is not an ellbow crusher at all. It simply - and safely - guides uke to roll forward. I actually have practiced this with a lot of beginners being tori. And I have fellt it, when I myself was a beginner.
If uke is more experienced you can also guide him to take a high fall.

This is, because the waza is not made to affect and destroy wrist or ellbow, but to use wrist and ellbow to affect and bend the torso, the body of uke.

Two more thoughts:
I have heard people from other styles who tried this way of shiho nage often say, it would be too soft and not "budô-like", because uke is only guided to the ground, but not "thrown". And that it lacks martial aspect, because neither ellbow nor wrist nor shoulder actually is attacked.
Plus: It is my experience, that Christian takes care of children and beginners a lot. It is his concern that everybody can enjoy practice. Literally everybody.
I've heard him scolding one of his students because he lacked caution.
I've more than once seen him working with beginners and also with children during his seminar. While his fifth and sixth dan students had to play with themselves ...

The experience that touched me most: There was a woman, practicing for about ten years or so. But still not being able to do a forward roll. Christian saw her, watched her taught her. After about twenty minutes she did her first forward roll ever. Years ago, but her smile I still warms my heart.
It was a seminar with maybe three hundred people or so ...

So, I'm not talking about the rights or wrongs of shiho nage here, but only about Christian as a teacher.