That report is a really enjoyable and honest read
it does suggest that a rotary design has a swept radius sweet spot …
Their tests with a single kite could not sweep a tight enough radius to be efficient.
Their analysis showed that sweeping too tight a radius with 2 kites linked at the tips is inefficient.
We’ve demonstrated that Kite rotors still work when you remove the central parts and replace the wing to wing connection with tensile line like the slightly later picture posted on tied flexible wing
That enables a tight autorotation with high speed on all blade elements and lower blockage with less chance of hitting your own wake