Are you sure your new panels are not sealed? Most of the new vest have sealed panels that are in a waterproof outer layer and are completely submersible. Most of the big name companies who are manufacturing to the latest testing standards are doing this on their own. Worth checking.
If you don't have that kind- its not the water that ruins a vest. Its the soap, fabric softener, tumbling and folding in the washer; and the heat/moisture of tumbling in the dryer. The vest is nothing but threads of Kevlar that coated and laminated through a weave into sheets. Sheets are rotated and stacked on top of each other.
The tumbling, bending and rotating from a washing machine does not mimic real life activities. These vest are stiff for a reason. Add in it not only bending, but the soap and fabric softener weakens the laminate threads bonding to each other. It wears and eats away at the laminate and thins it. Once it wears, the threads don't bod to each other nor have their stiffness. The once stiff solid and flat sheet of fabric now as a weak spot. The dryer adds heat and water and steam further ruins the bond in each sheet and between layers.
Will it still be OK? Sure- but no manufacturer will warranty such or be liable should it fail. Murphy's law is never on our side when we get shot- getting hot in the side gap, just above or below the vest, etc... What are the chance a round hits a weak spot and penetrates? Gamble some would take- others would not.