Additivity conjecture for the Morse-Novikov number under connected sum of links

Let $L_1$ and $L_2$ be links, and let $L=L_1\mathbin{\#}L_2$ be their connected sum. Let $\xi\in H^1(E(L))$ be a regular class whose restrictions $\xi_1$ and $\xi_2$ to $E(L_1)$ and $E(L_2)$ are regular.

Morse-Novikov additivity conjecture. One should have

$${\mathcal M}{\mathcal N}(L_1\mathbin{\#}L_2,\xi)={\mathcal M}{\mathcal N}(L_1,\xi_1)+{\mathcal M}{\mathcal N}(L_2,\xi_2).$$

This extends the known additivity statement for knots to regular cohomology classes on connected sums of links. The source presents it as a conjecture and gives no resolution.