This morning I got out for quick session and reminded myself to try this cast because I was on river right.
It's a interesting cast. A combo of double spey and high and slow but you're throwing a bit of energy into the D- loop.
Most of the time when I try a new cast it ends up being ok that works but it's a variation to a cast that loads the rod with similar energy.
This cast does give the D-loop a boost. It felt similar to shooting line on a single handed backcast.
Your rod is pretty much stopped in the firing position and your putting the D-loop energy into a stopped rod. When you come forward the energy is going deep into the blank. I even think it's easier to get the timing right over a standard double spey cast.
There is a more advanced version of this cast where you don't go into the double spey flop but instead you bring the rod across your back left shoulder and your anchor is placed behind you and then go into a similar sweep. This cast is easier to setup because it's hard to screw up the double spey anchor flop.
Try it out and have fun.