Equal-degree dimension conjecture for good determinantal schemes

Let $W(\underline{0};\underline{d})$ be the locus of good determinantal schemes in $\mathbb{P}^{n+c}$ of codimension $c$ given by the maximal minors of a $t\times(t+c-1)$ matrix whose entries are homogeneous forms of degree $d$. Equal-degree dimension conjecture. Then

$$\dim W(\underline{0};\underline{d})=t(t+c-1)\binom{d+n+c}{n+c}-t^2-(t+c-1)^2+1.$$

This is presented as a more precise special case that the authors would like to establish, namely the equal-degree case of the preceding dimension conjecture. Its status is not resolved in the supplied text.