Root conjecture for 2-twist spins of torus knots

Let $T(2,p)$ denote the $(2,p)$-torus knot, and let $K_p$ be its 2-twist spin. A knot is a root of the ribbon concordance graph if no distinct knot ribbon-concords to it from below. Root conjecture. For $p$ prime, the 2-twist spin $K_p$ of $T(2,p)$ is a root of the ribbon concordance graph. The preceding discussion gives supporting evidence through the structure of its knot group, but the source does not state that the claim has been proved.