The upper-bound conjecture for maximal Fourier coefficients

Let $G$ be an $F$-quasisplit classical group, let $\psi\in\widetilde\Psi_2(G)$ be a global Arthur parameter, and let $\widetilde\Pi_\psi(\epsilon_\psi)$ be its automorphic $L^2$-packet. Let $\underline p(\psi)$ be the partition attached to $(\psi,G^\vee(\mathbb C))$. Upper-bound conjecture for maximal Fourier coefficients. For every $\pi\in\widetilde\Pi_\psi(\epsilon_\psi)$, the maximal Fourier-coefficient partition satisfies

$$\mathfrak n^m(\pi)\leq\eta_{\mathfrak g^\vee,\mathfrak g}(\underline p(\psi)).$$

The claim relates Fourier coefficients of Arthur-packet members to Barbasch–Vogan duality. The source states that determining the exact partitions remains open, while proving the bound for all parameters is not asserted there.