So, how did you do that thing without breaking your metatarsals? And is your upper body made out of antigravity? The mechanical advantage for that particular movement is really low.
I don't recommend it. I used to love lying back in SEIZA and just feeling the stretch. It wasn't until decades after I started doing it that I realized it was hurting my knees. When I stopped doing it, my knees stopped hurting.
But, fwiw, it was a combination of two practices. 1) Sitting up while lying in SEIZA; 2) learning to control various stages of that back arch which I did through UKEMI for SHIHOO NAGE. Get the proper momentum with the inital rise, and the rest of it just sort of comes. The first time I did it I surprised myself.