Using voxel remesh with multires rebuild makes a different mesh. Said mesh is full of loops that aren’t there when remeshing with no multires. The loops make the surface look full of sharp spots when the polycounts is high
Here are examples of what i mean
Those are poles created when edge loops change direction, which is something that every subD modeler has to contend with unfortunately. Subdividing those poles is what causes the “pinching”.
You could try messing around with the resolution and rebuild levels to try to find a sweet spot to reduce the number of poles the algorithm has to make.
Maybe try adding 3-5 levels to get a lower poly base level (you might need to increase the resolution of the original mesh though).
