Positive-Ricci-curvature conjecture for parabolic geometries

Let $G$ be the split real form of a semisimple Lie group with parabolic subgroup $P$, and let $P\to E\to M$ be a $G/P$-geometry. Suppose that the Lie algebra $\mathfrak{g}$ has its parabolic filtration with $\mathfrak{p}=\mathfrak{g}^0$, inducing a subbundle $E\times_P V_1\subset TM$, where $V_1$ is the first filtered piece. Choose a principal maximal compact-subgroup reduction $E^c\to M$, and let it induce the canonical Riemannian metric on $M$. Positive-Ricci completeness conjecture. If this Riemannian metric has positive Ricci curvature along $E\times_P V_1$, then the $G/P$-geometry is complete. The claim proposes a geometric completeness criterion based on Ricci curvature in the distinguished filtered directions; the supplied text gives no resolution.