Categoroid equivalence between Poisson manifolds and regular relational symplectic groupoids

Let $\textbf{Poiss}^{Ext}$ denote the categoroid whose objects are Poisson manifolds and whose morphisms are immersed coisotropic submanifolds, viewed as coisotropic relations. Let $\textbf{RRSGpd}$ denote the categoroid of regular relational symplectic groupoids.

Categoroid equivalence conjecture. There is an equivalence of categoroids between $\textbf{Poiss}^{Ext}$ and $\textbf{RRSGpd}$:

$$\textbf{Poiss}^{Ext}\simeq\textbf{RRSGpd}.$$

This conjecture proposes a categorical relationship between Poisson manifolds with coisotropic relations and regular relational symplectic groupoids; the source gives no resolution or further established form of the relationship.