Zhuang–Gao conjecture on the Gao constant

Let $G$ be a finite group. Write ${\sf d}(G)$ for the smallest integer such that every sequence over $G$ of length at least ${\sf d}(G)+1$ has a nonempty product-one subsequence, and write ${\sf E}(G)$ for the smallest integer such that every sequence over $G$ of length at least ${\sf E}(G)$ has a product-one subsequence of length $|G|$. Zhuang–Gao conjecture. For every finite group $G$,

$${\sf E}(G)={\sf d}(G)+|G|.$$

The inequality ${\sf E}(G)\geq {\sf d}(G)+|G|$ is known in general, while equality is established for several families of groups. The conjecture remains open in the generality stated in the supplied source.