The integral homology conjecture for the graph complexes $\mathcal{G}^1_n(X)$ and $\mathcal{G}_n(X)$

Let $\mathcal{G}^1_n(X)$ and $\mathcal{G}_n(X)$ be the graph complexes appearing in the integral calculation for $\operatorname{Out}(F_n)$, with the natural map

$$\mathcal{G}^1_n(X)\longrightarrow \mathcal{G}_n(X).$$

Integral homology conjecture. The map $\mathcal{G}^1_n(X)\to\mathcal{G}_n(X)$ induces an isomorphism on homology in degrees $2*\leq n-3$.

This conjecture would strengthen the corresponding result with $\mathbb{Z}[\tfrac{1}{n-1}]$-module coefficients to integral coefficients. The supplied text does not state whether it has been resolved.