The conjectural formula for the top-degree double ramification cycle coefficient

Let $\overline{\mathcal{M}}_{g,2}$ be the moduli space of stable curves with two marked points, let $\lambda_g$ denote the top Chern class of the Hodge bundle, and let $\mathrm{DR}_g(a,-a)$ be the double ramification cycle with weights $a$ and $-a$. Let ${\mathsf{B}}^g$ be the tautological class defined by the alternating sum of decorated boundary strata described above. The conjectural formula.

$$\operatorname{Coef}_{a^{2g}}\,\mathrm{DR}_g(a,-a)\lambda_g={\mathsf{B}}^g.$$

This gives a conjectural expression for the coefficient of $a^{2g}$ in the product of the double ramification cycle with the Hodge class, in terms of tautological boundary classes. The source attributes the formulation to earlier work, but the supplied text gives no evidence that the formula has been proved or disproved.