I moved my sedirea japonica into s/h and it has been one happy plant. It popped a spike before it popped anything else. In fact, I may have been premature in moving it into s/h but that has not made any difference. It loves s/h. It has now sprouted new roots that are headed toward the leca. It has not yet added any leaves but that will happen after this spike has finished flowering. It should be open in a week or less I'm guessing.
My plant had less roots than what I see in your picture when I moved it into s/h. I think you'll find it takes to s/h well. At least that is my experience.