Liu's conjecture on gap-level excedance and Denert statistics

Let $g\geq 1$ and $\ell\geq 1$, and let $g\mathsf{exc}_\ell$ and $g\mathsf{den}_\ell$ denote the $g$-gap $\ell$-level excedance number and $g$-gap $\ell$-level Denert statistic, respectively. Set $r=g+\ell-1$. A pair of permutation statistics is $r$-Euler-Mahonian when its bivariate distribution over $\mathfrak{S}_n$ agrees with that of $(r\mathsf{des},r\mathsf{maj})$. Liu's conjecture. For all $g\geq 1$ and $\ell\geq 1$, the pair $(g\mathsf{exc}_\ell,g\mathsf{den}_\ell)$ is $r$-Euler-Mahonian, where $r=g+\ell-1$. The paper's abstract says that its main objective is to confirm this conjecture, and the supplied proof passage says that a bijective proof is obtained; however, no explicit status evidence field is supplied for this candidate.