Partially removing the divider wall makes each bank draw from both left & right sides of both carburetors (the reverse of why 180° manifolds are used). Vacuum signal is reduced, not with this design but any wall height reduction.
Since the manifold itself does not have equal air flow to each port (unavoidable with dual-plane manifolds - read some of Vizard's tests showing as much as 50 CFM difference between high and low) even the original fuel distribution is now gone. The WOT can be made closer by stagger jetting, front-rear bias, HSAB experiments, but not the A:F balance to each cylinder.