WOW! I love this invisible double knot!
I envision many cases where this knot will work wonderfully. However, she used the knot on garter stitch, the most forgiving pattern stitch IMO.
If I was using Debbie Bliss 100% pure silk or dk cotton with stocking stitch, I wouldn't use this double knot join in the middle of the work. Maybe at the end, near the edges.